I can attest that a night at Mayaland is very cool. The grounds, the cottage with thatched roof yet all modern amenities, the food isn't bad either. The lobby door looks out at the observatory at the ruins and the walk through the jungle to the night light show (it's in Spanish so brush up) at the great pyramid is a favorite memory- I thought it was like something at Disney, then it dawned on me that this was REAL!
As to the drive, we took the toll road to/from Cancun which is decidedly uninteresting. On the drive back, we went to the central market in Merida, knowing we wouldn't likely be any closer.
The tour buses take the free road through Valladolid and stop there. Must be something there, but I have no first hand knowledge. There are also cenotes say: sen-oh-tay, for swimming here and there in the jungle. There are maps of their locations.
Take the toll road in the morning and drive directly to Chichen Itza (expensive, and have lots of change in pesos) The Mayaland is a beautiful hotel, (reservations please). If you stay there you can walk across the street to the back entrance of the ruins and spend most of the day. The food at the Mayaland is good, and they usually have entertainment. You can catch the night show at the ruins if you stay overnight. If the Mayaland is full you may wish to try the Hacienda Chichen. There are many restaurants in Piste, which is the town nearest to the ruins, which you may also which to visit.( tourist shopping) There is really not much to see along the way on the toll road, but, the next day if you return to Cancun you can take the slow road, and go to the city of Valladolid which is quite interesting. There are a lot of topes (speed bumps) on the old highway, which make going slow, but interesting...don't drive in the dark.
The cenotes are all connected by underground rivers that traverse the entire area, so the water is constantly changing. They are not simply stagnant ponds. That is why they are so cold. I wouldn't worry about the bacterial content, when swimming. The same fresh water is is filtered and used in the hotels, so if you can drink it, I imagine you can swim in it...
We went cenote swimming a few years ago while spending a week in Yucatan. They are not a problem, very refreshing on a hot summer day. I would highly recommend vising Uxmal. We enjoyed it much more than Chichen Itza. No crowds! Utterly fantastic carvings.
We hired a local guide for the two of us for 500 pesos -it was well spent. He explained so much more than what you can see on your own, answered any questions we had, was in no rush what so ever and used the experience to work on his English, which was very good to begin with. I think Uxmal was the highlight of the 1/2 dozen ruins we visited that trip.