Continental has direct flights to Belize from EWR (Newark) on Saturdays. I was lucky enough to get on one on one of my trips and what an easy trip that was..Back to Jersey in 4 to 5 hours or so!! There was talk that they were going to expand that service to other days.
Will check with friend from Continental on the Denver/Cleveland -Belize "rumour" to see if she's heard some buzz.