There are two options: you can fly with Maya Island Air. Their website is www.mayaislandair.com and they depart Cancun at 2 pm on Dec 13 and arrive Belize at 3:20 pm, cost is $199 US one way plus tax. Or you can take the bus. First you have to get from Cancun airport to Cancun bus terminal: click here for details: http://www.cancun-airport.com/public-buses.htm Then you take a bus from Cancun to Chetumal. There is a departure at 9:30 am and 10:30 am on Dec. 13, cost is 258 pesos, it takes 6 hours. From Chetumal you take a bus to Belize City, I don't have the schedules. Check this website: http://www.travelnotes.org/LatinAmerica/belize.htm where they also mention 2 other airlines and more info about the bus, perhaps you can contact them for more details. Happy travels!