DH and I are going on a much needed vacation in May. We met with a travel agent and explained what we were looking for in a vacation and she suggested Cancun or Riviera Maya. She priced some AI resorts that were in our price range, and now we're trying to pick between them.
What we are looking for in a vacation - beach, water activities (maybe sailing, snorkeling, possibly SCUBA). We like to explore, and would be open to going outside the resort, but it's not really necessary. We've thought about visiting Cozumel while we're in the area, which I understand is a ferry ride away. We're not really club/party people and are usually in bed by 10pm, but we like to people watch and see cultural/historic sites.
The resorts she selected are the Sun Palace (Cancun) and Moon Palace (Riviera Maya), which are both offering a $1500 credit toward spa, room upgrade, excursions etc. And Riu resorts (Palace Mexico and Palace Riviera Maya). All seem to have good reviews on Tripadvisor and all have things to offer, but I can't pick between them.
Anyone have any insights on these two areas and/or the resorts to help me narrow it down? Thanks!

Re: Cancun vs Riviera Maya, Palace resorts vs Riu
I would definitely pick Sun Palace over Moon Palace. Sun is an all adult, smaller, more intimate resort on a great stretch of beach. We have been to Sun several times and have always enjoyed our vacations there.
I have not stayed at Moon Palace but have gone over for day trips for golf. While we enjoyed the golf, we did not like the resort. It is a very large family resort. When we have gone there, the pools were noisy and crowded and kids all over the place, including running around the lobby. The beach is not as nice as Sun Palace. Also if you wanted to go into Cancun for nightlife, shopping, etc. it would be about a 20 minute cab ride.
Sorry, can't help on RIU resorts, never stayed there before. We have stayed in RM and it is closer to Mayan ruins and ferry to Cozumel from Playacar.
Have fun!
I love the Mexican Riviera, it's one of our favorite places to visit! I would recommend something outside of the Cancun hotel zone, there isn't much "culture" in that area, just tons of people/cars/buses/mopeds. The first time we went to that area, we stayed right downtown in Playa Del Carmen which was so fun. We stayed in a little boutique hotel called Kinbe, it was a minute walk to the beach or to fifth ave. It is a perfect location, you can walk to the Cozumel ferry or the bus station, if you're not renting a car.
We've also stayed just south of Playa in a large gated community, called Playcar. We stayed at Sandos Playacar Riviera, it's a beautiful hotel. HUGE. Great food, drinks, activities/shows and staff.
My favorite things to do in that area are...
The ruins at Coba, they are totally different from the other big sites in the Yucatan, less crowded and just an overall way better experience than Chich?n Itz?.
The ruins in Tulum are amazing as well, make sure you go early in the AM to beat the tour buses and bring your swimsuit, there is awesome swimming there.
Snorkeling at Corona beach on Cozumel and the lagoon in Akumal.
Valldolid is an amazing colonial city as well as Merida if you have the chance to get out and explore the less tourist stuff.
I could go on and on about this area, I just love it so much! Have a great trip! I liked staying at the non all inclusive more so than they AI because we were able to try so many different restaurants in town. If you're not a big drinker, I don't think an AI is really needed for the Playa area. Sorry this is so lengthy!
fyi nov: the mexican riviera is on the WEST coast, riviera maya is on the EAST coast
OP-if you like to get out an explore (i'm not sure if you mean a town or day trip but I will answer for the town) i suggest staying IN playa del carmen or cancun. the down side of many AIs in riviera maya is that playa can be a very lengthy cab ride into town. Playa is super built up too. If you're looking for a super laid back place the town of tulum is good. but it's also VERY VERY small.
We stayed at one of the RIU cancun resorts in March 2010....and it was pure craziness. There were TONS of spring breakers and annoying rowdy people. I was really dissapointed because I read that there shouldn't be too much of that at our particular resort since there were so many cheaper options that the spring break crowd was thought to be at.
I have heard awesome things about Sun Palace...and I think that is your best option going as a couple!
We went to Chichen Itza and it was really awesome to see. It was FREAKIN HOT though even in March (and I am a Floridian, I am used to heat). I literally blacked out and thought I was going to die (I was pregnant too). So bring lots and lots of water or lots of cash to buy water!!!!