The wife and I use cheapcaribbean.com and pick the adult only all inclusive “Deal of Fortune” where they pick the resort. The area you’re interested. The resort has to be 5-star all inclusive. We’ve done it for Cabo, Riviera Maya, and Jamaica with good results. They always put us in a Secrets, and we got significant room upgrades on two of the three. The one time we didn’t, the resort was at capacity.
If you do enough research on the areas and message boards, you can narrow down the hotel choices they will pick. Each time, we were comfortable with the choices, so it wasn’t a big deal. It also adds an element of surprise and excitement for the trip, as you typically don’t find out until the day you leave.
I forgot how much we saved doing the “Deal of Fortune”, but I think it was around $400 per person.
Of all the locations, Riviera Maya was the best bang for money.