If you fly into cancun you can catch an airconditioned bus to Chetumal which is on the border with Belize, it costs about 21 or 22 US dollars one way, then you have to get to Corazal town on the belize side and you can either fly from there or take a water taxi. Its not a difficult trip and will take you about 8 to 9 hours from Cancun to Sanpedro if you time your transportation right.

Reality..What a concept!