Any advice on where to locate?

It depends on what you are looking for:
Corozal/Orange Walk district - mostly flat with some rolling hills, close to the sea, close to Mexico, close to the major cayes, a lot of farming in the area (lots of farming all over Belize).
Belize district - rolling hills, lots of rivers, borders the sea, includes Belize City which you might want to mostly avoid, the airport, and water taxis to the cayes.
Stann Creek- includes a lot of the Maya mountains, a number of forest reserves, half of the Hummingbird Hwy, Hopkins, and a lot of the 'inland' coast, a lot of farming.
Cayo- also includes a lot of the Maya mountains, the other half of the H'bird Hwy, Belmopan, Spanish Lookout (Mennonite community), San Ignacio, a lot of farming.
Toledo- the southernmost district, includes Maya mountains, a fair amount of the coast that is partly south of the barrier reef, the Placencia peninsula, Punta Gorda, lots of rivers, the Belize Spice Farm. Probably the least populated district.
The cayes- diving, snorkeling, fishing,  water sports, beaching
All the districts are 'different' in geography, terrain, population.
There are resorts and lodging options in all the districts.
This forum contains a lot of information; you may need to use the search function and/or read old threads. You might also consider a book like Frommer's or Fodor's for general information.