For our short (6 day) stay in Vietnam, Hitomi and I were on a 4 day tour with Sinh Balo to tour the Mekong Delta.
The tour included a driver (driving the SAG wagon) and an English-speaking bicyclist would lead our group. We had an excellent time, but I won't detail the specific trip itself too much, I just had the following thoughts on cycling in Vietnam.
Traffic in Vietnam
One of the first concerns you have as a cyclist is of course safety and when going to a foreign country it's not just (at all?) a matter of understanding the rules of the road, but following the actual practice of traffic.
Apart from occasional stop lights, traffic would continuously flow seemingly without concern of volume or density. Vehicles would freely pass each other onto oncoming traffic. Horn noises would be exchanged constantly as part of passing etiquette. There were tens of motorbikes for each car and left turning, right turning, and forwarding moving waves of them would weave around each other. And as well, because of no sidewalks, large numbers of pedestrians were really part of the traffic flow as well. Let's not also forget the innumerable cyclists, some of them pulling large trailers or what have you, and huge farm trucks. Really what was intimidating was how closely vehicles moved together but there weren't too many people speeding. Car and truck drivers had to always be paying attention, because the road ahead was very rarely open for more than a hundred meters.
Ironically, I felt pretty safe in Vietnam, because it wasn't 99% cars and 1% other traffic. It was maybe 85% motorbikes, 8% cars, 2% trucks, and 5% bicyclists and pedestrians. And most motorbikes went 25-30 miles per hour, and as a 15-20mph cyclist I wasn't completely outclassed. In the cities, I could fold into the motorbike traffic quite easily.
Christmas day, I rolled through the center of town with our ride leader Ngi. Other motorbikes were impressed that a foreigner such as myself could blend in so seamlessly with the traffic.
Roads in Vietnam
We were riding in the Mekong Delta, mostly, which meant aside from bridges over canals, we were on flat surfaces. Roads were relatively flat, though, as the pavement was never that smooth or, worse, hard clay and large rocks. Most major roads were being repaired or rebuilt. With my 23mm tires, I had 4 flats, mainly from the slamming my tires and wheels took. Luckily, there was always some motorbike shop just around the corner capable of repairing my tube for less than a dollar. (Incidentally, some major intersections in Ho Chi Minh City had roadside motorbike mechanics staked out, with a tub of water, spare tires, and a toolkit. With the thousands (millions?) of passing vehicles, it was fairly good odds someone would run into trouble.)
Why 23mm tires? Well, I brought along my road bicycle (Ritchey Break-Away) and with larger tires the wheels won't fit in the case. But I ought to have spent some money on 28mm heavy-duty tires and gone through the trouble to change them at the hotel. Since you're never going to find good pavement anyway, you might as well pack heavy-duty tires for comfort. Bring a good pump as well, as 7 bars of pressure (100 psi) is hard to come by from those motorbike shops.
All the construction I assume is because the local economy is taking off there and thus the need for better and wider roads.
Expect a lot of fine dust and sand crossing construction areas. Dust collects on your chain and bicycle parts. Locals helpfully douse their adjacent sections of road with water, which does cut down on dust. Some people wear masks.
Places to Ride
The tour took us to the best places to ride, I assume. My favorite was riding on an island on a 6-foot wide "road" through farms, the road under a canopy of various fruit trees.
Without many hills, if you're riding in the Mekong Delta, you're mostly looking at rice paddies, fruit trees, temples, and buildings in town. It's a delta! We did get to experience some hills in the Upper Mekong.
Riding in Vietnam, even in Winter, is hot and the shade is welcome relief. So, I preferred shady routes. One particularly nice stretch took us along 6' wide canals ("local streets") on even narrower roads. Hundreds of small bridges with no railing — don't fall over crossing! — make it a little scary at first. Expect to be spotted by children in their homes, shouting "Hello!" to you, especially if you look like a tourist. Oftentimes you don't actually see the children through the thicket, but somehow they see your helmet and jersey or large nose. Teenagers don't say "Hello" but you'll get laughed about if there's a pack of them.
When and How to Ride
Riding really hard during the middle of the day is likely to give you heat stroke, so ride early or late. We were with a couple who weren't interested in early departure, unfortunately. Such is the nature of group trips.
I found that riding at 14-16 miles per hour was probably the optimal. You develop a significant head wind but, assuming you're in decent shape, you don't get too sweaty. Bring gloves and a hat. I didn't ride with a helmet always and instead I rode with a wide brimmed hat for shade.
I liked having clipless pedals since when you're pedaling over rocky areas they give you better control. Consider bringing your own pedals and shoes if you're touring with a company's bicycle. I was considering those Shimano bicycle sandals, which would have been nice since I was always wearing sandals anytime off the bicycle.
Food and Lodging
I guess a lot of warnings go out about not eating fresh vegetables in Vietnam, but on the tour I they were put in front of us every meal, so we had them anyway. I found southern cooking was fairly sweet and not very salty, and if you sweat a lot you need to eat more salt. The German couple we were with made a fuss about salt causing high blood pressure, but you'll get headaches and feel sick without some sodium.
The nicest place we stayed was called a "homestay" by our guide but was probably more accurately described as a "pension" or in Japanese "minshuku". These you find out of the cities, which are nicer for riding, in my opinion. In cities, the hotels always seemed sterile and minimalist. All the places we stayed at lacked any wall or alarm clock, which is strange, so bring your own clock. All the hotels we stayed at had Westerns or other Asian tourists eating breakfast at the hotel restaurant. Expect lots of French bread and fried eggs for breakfast, with spreadable cheeses, bland ham or wieners; or alternatively rice "gruel" or noodles.
Fresh fruit is always in season, though not always the same fruits. Mango was ready, along with pineapple, "dragon fruit", bananas, and several local fruits I did not learn the names of. Expect to eat fruit for dessert. We didn't try too many local desserts; most Western desserts seemed overly sweet.
During the tour, we went to a gator farm, a hill overlooking the Cambodia border, various Khmer temples, fish farms under people's floating homes, farmers' wholesale markets on the water, an enclave of Muslim Vietnamese, various ferries, humongous roadside kilns baking bricks, and numerous roadside karaoke/refreshment stops. Speaking of karaoke, it is perfectly acceptable to sing karaoke at night, outside, amplified by loud speakers.
Thoughts on a Return to Vietnam?
A tour guide, or at least ground transportation like a car is necessary for getting comfortably out of Saigon. So, join a tour, but if you can afford it, go alone with a dedicated, small group.
Start cycling at 6AM, if you are going for any distance. Though breakfast is usually worth spending some time enjoying, take an after lunch nap instead.
The North is allegedly quite rainy and cold (cool?) during New Year's, so I'm not sure a tour in the North would be a good idea still, but some more varied terrain would have been nice. The only major climbing I did was a 400-meter-high nob along the Cambodian border, where the flat part of Vietnam turns into wild hills.
Other than a few comfort issues and tube punctures, I really enjoyed my trip. But one more tip: Bring a set of earplugs for the evening, just in case you're across the street from karaoke party.