There are two. In big cities like Saigon, Ha Noi, Hue, Vung Tau, Da Nang. There are meter taxis. Taxis are available at all airport. Sleeping berths are arranged in a compartment for 4 people.
Local people prefer motorcycles and bicycles due to narrow streets.
For the more adventurous tourists bicycles and motorcycles can be hired. Available at all river ports with reasonable prices. Water Drink only boiled water and be cautious when having ice in your drinks. Bottled water is common and dirt cheap at the market or small restaurants.