I just got back from Playa Del Carmen, Isla Mujeres, and also stayed in the Xcarat resort area.
Isla Mujeres beats all of the above, 10x fold.
Undoubfly, you're going to be steered to somewhere on 5th Ave, which is touristy as touristy gets. You're going to be bombarded every 10-20 seconds when you're just trying to mind your business. Just a warning. Personally, I hate 5th avenue and avoid it like the plague.
For drinks, expect to pay a pretty penny. They're not cheap, average is going to be $12-15USD on 5th avenue for a mixed drink. Many places will have "2x1" signs but be very careful what they truly mean by that. Usually it means for one person, not you and the wife. I just found out it also means that you have to order the same exact drink twice, even if both drinks applied to the price. Stupid as sin. I got totally ripped off
The place that did it to me was La Vagabunda De La 38, which isn't even on 5th ave. Food sucked, drinks sucked, and my bill for a late night snack + a few drinks was $75 USD. Never again (beware, they have a location on 5th as well).
For the same price, we had a VERY nice dinner, with better drinks, in front of a cenote on 5th. I recommend going to Aldea Corazon. If they don't have a 2x1 sign in front, just ask them to give you the deal and they will.
IMO, we recommend going to 25th Avenida nte / Benito Ave (it's the main section in town) and hit the local taco trucks. $2 a taco and beats anything else there.
You can drink on the streets there. Just do that rather than spending $15 on a drink!
The best "local" restraunt if you want to go sit down and eat is going to be El Fogón (we heard this over and over again).