For Mexico these places are extremely high on our list, Ocean Coral and Turquesa in Puerto Morelos or Barcelo Maya & Caribe by Play del Carmen, however you’re a little behind the curve for planning and airfare is going to be an arm, a leg and maybe even a testicle this late.
However I would seriously look in to Jamaica, been there a couple of times and hands down better then Mexico, have stayed on the Ocho Rios side and the Negril side and Negril is far better, Jamaica is the place to go to relax…I know they have a great Olympic sprinting team, but I personally have never seen a Jamaican run, or move fast everybody is extremely laid back and relaxed.