I love Mexico. In the more remote areas the food is limited and accommodations are less than ideal. Both are very inexpensive but not nearly as good as the larger cities. That being said the Mayan sites are amazing. The tourist hordes from the coast do not go to far inland. Chichen Itza, Tulum and Coba are the tourist traps. They are worth visiting too but know you need to arrive when they open for the best visit. Staying inland off the coast will help you get to them early. Uxmal has 4 sites close that are amazing and not to far from Merida. Santa Elana would be a better place to stay - the Flycatcher and the Pickled onion are the best places in town.
Xpujil is the place for the southern Mayan sites. We rented a car for two weeks from ISIS Rentaria. Yes I know, but they have been around for 20 years and were the best place to get a car. We read a few Internet posts about the police. The only officer who spoke to us just asked how we were enjoying Mexico, looked into an empty back seat and said have a nice day. Every check point we hit we were waved right through with no trouble at all. It was fun to be in Mayan ruin site almost alone. We saw 13 sites in our 12 days on the road. Mexico is fun.
Cozumel is fun to visit for snorkeling and diving. Playa Del Carmen has better beaches and people watching. We spent a week in Cozumel, 3 days in Playa Del Carmen and 4 days in Cancun. I would skip Cancun and stay in Playa if I did it again. Although we surfed in Cancun. Okay we took surfing lessons and were able to get up on the long boards. It was fun and it was a workout. I would definitely do that again.
We love Mexico. We have been there 6 or 7 times and will go back. Living in Portland now I may want to go back more often - warm sunshine and beaches await.
My photo and blog site for my 2016 travels and beyond
P.S. If you go to the destination page and click the link to locations, I share pictures from each trip