Until December 13, it is low seasson, as schools in Mexico are still active. You will not have a problem finding cheap acommodation. If you want to fly there, try VivaAerobus.com.mx or Volaris.com.mx, the cheapest options. Try to avoid AM, as their Gran Plan combos are expensive. Go better with Interjet´s Intertours, for a Flight + Hotel deal, either in CUN or Riviera Maya.

You will for sure have to fly from MEX or TLC to CUN, as flights to Chetumal (if you want to go to Belize) are a lot more expensive, as only 1 airline serves the area (Aviacsa and Mexicana use to serve it, but they are gone). Belize from MEX, forget it, there aren´t flights from Mexico´s Capital City.

If you get cheap airline tickets from the LCC, then getting hotel deals before December 13 will be really easy. Try some Spanish All Inclusives in Riviera Maya, you will be amazed about the quality of its food, drinks and service. Riu, Iberostar or Barcelo Premium are some of the best out there.