I agree, Mopan River Resort is wonderful. It's right on the Guatemalan border so it is is the closest Belizean resort to Tikal. There is one problem with keeping your windows open at night, however, and that is they are still open first thing in the morning! Anyone who has been there knows what I mean http://www.mopanriverresort.com/
...and if you are doing your research by town name you'll have to look for Benque Viejo del Carmen.