Excellent advice - Doc V writes for undercurrent, so his view might lean that way just a tad, but I don't, and my view says Undercurrent is the only truly reliable source of information in wide distribution.DocVikingo once bubbled...
consult the latest edition of Undercurrent's "The Travelin' Diver's Chap Book" http://www.undercurrent.org/ . No ads, no BS.
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Now, as to a specific recommendation, your description of what you're looking for sounds to me like the "Mayan Riviera" - and my specific recommendation would be Villas de Rosa, between Akumal & Tulum.
Rick