beach vacation ideas

So after a divorce and a couple financially tough years I'm getting back on my feet and thinking about a warm get away this winter.I've been to Mexico and costa Rica.when in costa Rica both times we were in Tamarindo.the first time was awesome ! Second time there the commercialization had taken over.
I'm looking for nice beach and nice accommodations but looking for more of a low key atmosphere with some decent nightlife/restaurants near by?
Who can recommend something in Mexico or central America? Maybe Colombia?
Thanks for any help!