It's really hard to write a small post about food in three different areas, which is the reason why I'm just going to mention about what is most popular in these places and hope it can give you an idea. A very special point which makes the south of Vietnam different is that the people down there cook with lots of sugar, and in the north it's too much MSG. In the centre of the country, people cook with lots of salt or fish sauce.
In Ho Chi Minh City, most people go out for an easy and quick lunch then go back to the office or go home for a nap before heading back for work again. I think Bun Mam is one of the most popular dishes in Sai Gon which can be eaten everywhere, even sitting on the street? Why not, or even in a restaurant, this is the dish that lots of people choose whenever they come to Saigon.
In Hanoi, people are more used to eating at home. After work, people hurriedly go to the market to buy some food and go home, cook and eat with their family. This is a good thing to do, but it's time consuming. However, a popular dish to have out of the home in Hanoi is Pho Ga (Noodles with chicken), the special point of which is that people can eat it as a snack or as the main course, and the location is not a problem at all.
Similarly to Hanoians, Nha Trang people tend to have three meals per day at home. But when they go out to eat Nem Ninh Hoa (Ninh Hoa spring rolls) is the most famous that everyone knows about, cheap and good. It doesn't matter whether it's lunch or dinner because it's a really healthy dish with lots of veggies.
I think people have started eating out for lunch more now in big cities, or they're prepared food for the whole day in the morning, so that they can save their time and they still can enjoy their meals at home. Vietnamese people usually take a short nap after lunch and that's why there is little action on the street at lunch time.
Labels: Restaurants - Ho Chi Minh City, Restaurants -Ha Noi, Restaurants -Nha Trang, Travel