If you want to be in town. Check out the Palms at http://belizepalms.com/packages.html
They have special packages starting in May that run about $100 a night when you consider the package includes your transfers to and from BC.
I think Belizean Reef (another nice place, but no pool) next door to the Palms also has great rates at this time. Have a great trip no matter where you choose to stay. mobunny