Exotic Caye is a good cross between classy and affordable. Out of season they have been giving very good rates. They have a pool, a drinking bar and an excellent snack bar on the premises, and they're only 10-15 minutes walk down the beach from the centre of town. A good choice. You won't go wrong with Amigos, though some other dive centres are also worth considering. Citing some well regarded ones, geographically Amigos is at the other end of town, Ecologic is a bit further still (though both will of course pick you up), and my establishment is very close. Search on these names to see what people think of us all. There are also several other excellent operators you won't have heard of, so maybe the thing to do is not book your dive operator in advance but do a quick review once you get here - no operator will be full at that time.