Figured that this would be perfect opportunity for 1st post. Just retuned last night from 5 days 4 nights at Secrets Capri in Playa Del Carmen. Can't say enough about the place. Sounds perfect for what you are looking for. All-inclusive with no kids. Awesome place for lounging around the pool or walking on the beach. Service is 1st class and booze is top shelf.
Tip the guys a few bucks and you will NEVER want for food or drink by the pool or beach.
2 downsides - beach is perfect for relaxing but not for swimming - too many stumps/rocks in the water. Dress for dinner is slacks and shirts for guys - not my favorite attire but the wife loved it and the reward was well worth the risk.
If you can afford the upgrade, book the JR Oceanfront Suite - you can throw a rock in the ocean and the room is perfect.
Cost me $2,200 from Atlanta for 4 nights and worth every penny...... If you want pics or info, let me know.