There will be many street vendors selling tacos and the like in the morning. Try them. While you are in Belize, be sure to have some salbutes - fried corncakes, tomatoes, chicken - available at a couple of places along main street. There are a lot of Chinese restaurants in Belize, and they are usually pretty good, especially the bigger ones.
Of course, the staple of Belizean cuisine is chicken - barbequed chicken, rice and beans, flour tortillas and potato salad.
One of the better places to eat in Orange Walk is the Lamanai Riverside Retreat. The menu emphasizes seafood. There are no vegetarian options on the menu, but the staff are happy to work out a vegetarian plate.
Panificadora La Popular
This bakery has been providing the town with fresh bread and tasty treats since 1955, and is definitely a favorite stop for the locals. They are best known for their abundant selection of Mexican-style sweet breads and pastries baked daily.
Sing Wong Chinese Restaurant
One of the oldest Chinese restaurants in town, offering great Chinese food, sea food and vegetarian dishes. Take out is available.