you could go to Caye Caulker, for a day, but just for your information that too is not cheap as you have to take a boat 30 min there, $35 US round trip. It is the next island over so not exactly something you can do daily and not much to do over there besides hangout on a lounge chair or eat. I'd suggest the Rainbow Cafe, the upstairs has a great view over the water. Much more economical than Rasta Pasta. I wish you luck on your budget there.