Do you want to buy food yourself or you are joining a local host for a home dinner? There's an activity in Saigon which you shouldn't miss. Anyways, Ben Thanh (Chợ Bến Thành) is easily recognizable by its clock tower at the main entrance. At District 1's Ben Thanh market there's nothing you can't buy. It is the most famous market of Saigon and a great activity to get the best price for the veggies you have in mind.
Visit the part with non-touristic items to get a feel of how locals do their shopping. You will find a lot of bargaining, so get ready to slide in the bidding battles. Make sure that you stay on top of the game with exact quantities, prices and exchange rates that can reduce your change. If you don't prefer to bargain, there are shops on the north side with prices listed, but less fun included.