International clinics in major cities offer the highest quality care but also cost more. Local hospitals are not quite up to the standards of Thailand, Hong Kong, or Singapore, but they are decent and often employ doctors who have been trained overseas, typically in France.
Temperatures in Vietnam can get extremely hot; make sure to drink plenty of water and use common sense to avoid dehydration, heatstroke, and sunstroke. Dengue fever and malaria are risks isolated to areas in the Central Highlands—if you’re not taking a prophylaxis, make sure to use mosquito repellent. Most of Vietnam is quite humid; keep a close eye on small cuts and scrapes as they can easily get infected.
About travel guide, using sunscreen is recommended, especially in the south or on the coast. Sunscreen is sold in more upscale pharmacies and in stores featuring imported products.
The language barrier is an issue in local hospitals, although some doctors can speak French. Pharmacies are plentiful and well stocked.
Street food is one of the more authentic ways to enjoy the Vietnam experience and is usually clean and tasty. If you do decide to indulge in frequent street dining, keep in mind the risk of parasitic infection from eating improperly handled meat.