Budget traveling, Belize?

Question

I'm heading to Belize with my girlfriend soon. We'll be there for nine days and plan on staying on Caye Corker. We're planning on snorkeling, checking out Mayan Ruins on the mainland and venturing to other islands for day trips. We're concerned with budgeting issues as we've planned on taking nearly 1000 dollars each and splitting all costs evenly. We've heard that cash is about the only payment accepted most places and that credit cards aren't! My question is that will 2000 between the two of us be enough to cover our expenses? We're planning on living modestly, hopefully under 30 a night and not splurging on unnecessary amenities. Are there hidden costs not mentioned in in the travel books? Has anyone done this similar thing? any help is GREATLY appreciated.