For US$65 a person, you can't go wrong! It's a full day that includes transportation, an awesome time at a cenote, lunch and shopping in a mayan village and finally the entire afternoon to explore chichen itza. The guides were excellent and share a lot of information. It's a great tour for people who love to learn about different cultures.
The actual ATV ride was about 45 mins but with transportation to and from, the entire thing was about a half day. The ride was fun. First you drive through a jungle type scene followed by sand dunes. And you go fast too!!! Not to mention it takes place on Maroma beach which is one of the most beautiful ones I have ever seen. Definitely don't do the ATV alone. Do multiple activities like speed boat or snorkelling. The place is worth spending the entire day there.