I spent a few days in interior Belize last year, which is probably very different from the most touristy coastal Belize. I arrived overland from Guatemala and continued overland into Mexico. I found it interesting culturally and the people were friendly.
I crossed into Belize near San Ignatio, then later went north to Orange Walk. I departed Belize by crossing into Mexico near Chetumal. I went on a very pretty boat excursion from Orange Walk upriver to an interesting Mayan site. There are several nature sites in western Belize which can be visited. If you're in western Belize, it's worthwhile going on a daytrip excusion to Tikal nearby in Guatemala, an enormous and very impressive Mayan site in a gorgeous tropical forest with lots of animals. I enjoyed it much more than the Mayan sites in the Mexican Yucatan.
I ate quite well in local places and prices were very reasonable.