Hi
I don't know how much time you have but you might consider splitting your trip between Caye Caulker and someplace near San Pedro. You can tour the ruins from CC but spend a lot of time travelling.

We split our last 9 day trip between the islands and the "jungle". Trip report and photos from both can be found on www.AlandSueJohnson.com
if you're interested.

We're going back to CC in Feb and can't wait.

Our Belize Trips and Pictures