I grew up in BZE:
If you are not into diving there are plenty of other things to do. Mayan Ruins, Caves, Rivers, Birding, Fishing, etc.
The mainland does not offer any beaches and stay away from BZE City.
Ambergris Caye which is where Ramons Villiage is definitely is a hot spot but the island is over priced and packed with tourists. If you want someting a bit more quiet, cheap, then go to the island next door, Caye Caulker. Plancencia is a great place as well. Punta Gorda is the farthest South but most quiet and laid back of the country. You can go across the bay (45 min boat ride) to Guatemala for the day from Punta Gorda.
Good luck...