More than you asked for, but I'm jonesing for the Yucatan Peninsula right now...
I grabbed a map. I read. I read some more. I asked people questions via private messages about the route. Going on your own is not without stress, but we enjoyed the adventure
I can't remember what car rental agency we used, but it was foolish of me to be sold on the "car delivered to your hotel" bit. We were picked up at the hotel - late, and then taken to the agency office for the usual paperwork. It would have been much more expeditious for us to walk to the agency and git er done. Other than that, no problems with the rental. Also keep in mind that rules of road the road in Mexico are different.
Keep in mind, we stayed overnight in Valladolid and visited Chichen early the next day. If we only had time for one day with no overnight outside of Playa, we would
definitely do a tour. It's nice to have some adventures on vacation, but relaxation is also a goal, yes? Then again, you might be younger than me.
If you visit ruins on your own
hire a guide. It's well worth it. My husband and I feel that the $60.00 US we paid for a guide, plus well deserved overtipping was some of the best money we ever spent in Mexico. I think the Yucatreks tour includes a guide,
a big plus. Friends of our visited Chichen years ago on a big bus tour. They were let loose and told when to be back at the bus...they missed a lot.
Would love to read about what you decide and your experiences!