we went the other direction.
flew to corozal, enjoyed a long lunch at tonys, had alvin leslie take us across the border to chetumal (your driver is a great help at the boarder crossing), spent a fun night in chetumal at cocos hotel (you can shop your butt off there too), take the primo clause (1st class) bus to playa del carmen. not a bad journey. good ac, american movie, functioning toilet. david, being 6'2" said that it did get a bit cramped but it is not a bad ride.