Joe, AC(Ambergris Caye) is an island, you either fly there from Belize City(BC) or Corozal or take "water taxi" from BC. The trip from Cancun to Chetumal will take 5 1/2 hours on what we call here "the highway of death", you read between the lines. Crossing from Mexico into Belize can take as few a 30 minutes or over 3 hours depending when you cross, there is a free trade zone just across the bridge in Belize, on week end there are bus tours from Cancun and Merida using the bridge. With a rent car I wouldn't try it, you must purchase Belize auto insurance before leaving the border area, the trip from the border to BC will take 2 hr. +. FYI, gas here in Mexico is $2.50/gal. A bus from Cancun to Chetumal is under $35 US roundtrip, bus from Chetumal from Chetumal to BC cost under $30 US round trip. Now how can we help you...?