The Villa Archeologicá (part of Club Med) has hotels at Chichén Itzá, Uxmal, and Cobá. I highly recommend them for their service and convenience of location. Being close to a site means you can easily be there when it opens (and so there are fewer tourists to deal with). You can also return to your hotel at any time to eat, get more supplies, or to rest, or whatever. This paragraph especially applies to the site of Tikal. If you can get a room in one of the few small hotels that exist in the Tikal park, do so. There's nothing like staying inside the park, where you can walk from your room directly to the ruins. You also can experience the sounds of the jungle at night in your room (the top third of our room was open screen, so the sounds of the birds and howler monkeys came right in!).