Chichen Itza is the most famous Mayan ruins in Mexico. It was a nice experience, but thousands of annoying souvenirs vendors occupied the site, and we couldn't climb any of the pyramids.
We based ourselves in Valladolid a beautiful cobbled street town not too far away from the ruins. There are cheap collectivos plying the route between Valladolid and Chicen Itza, which makes it an easy day trip. Just remember that the interior part of the Yucatan Peninsula is freaking hot. We barely survived the two nights we spent in a non-aircon room. That's the price you pay to save a few bucks.
As I already said, the Mayan Ruins of Chichen Itza is pretty nice. Especially the main pyramid is impressive, but it cannot be climbed. Bummer!! I think I like the Mayan ruins of Palenque better. Palenque is more peaceful and it's location in the jungle is much more spectacular.
Next stop is Cancun where I have to pick up my brand new passport which was stolen during an armed robbery outside of Mexico City.