You have to be careful when walking in towns like Hanoi and Ho Chi Minh City in Vietnam. Motorcycle cabs are the most convenient mode of transport here. Cross roads using pedestrian crossings if available or at intersections with traffic lights.
While in Vietnam preferring to eat in established good hotels or restaurants is the safest option. If you do wish to eat at roadside stalls and small eateries, avoid as best you can raw and cold foods. Refrain from drinking beer or soft drinks with ice in them.
Other sites include Ha Long Bay in Hanoi, Cu Chi Tunnels in Ho Chi Minh City, etc. In a group, these excursions will be a sure dabble. Also good for solo travels and companionship, as the local population is very friendly and accustomed to such arrangements.