Nate Bennett
Google
5 stars for the actual cenotes, as they were beautiful, clean and quiet. As others have mentioned, the "guides" feel somewhat scammy. I knew about them beforehand from these reviews, but when we actually got there it was hard to say no since we weren't exactly sure where to go right away and I didn't know who we needed to buy the tickets from. They tried to charge us 500 MXN after showing us where the cenote was.
So, say "no gracias" to everyone at the very front who greets you when you park, walk straight in and you'll see the area with booths to your left after a couple hundred feet where you can actually buy the tickets to get in. Once inside the little courtyard area, Xkeken is to your left (across the road) and Samula to the right. You'll have to get life jackets on the left side of the courtyard and leave an ID as collateral before going to the cenotes.
Also, I was a little confused about the different names on Google Maps (Dzitnup, Samula, Xkeken), but the individual cenotes here are Samula (smaller and shallower) and Xkeken (larger and deeper with cool cave formations), and Cenotes Dzitnup refers to them collectively. Both of the cenotes are very beautiful in their own ways and are well worth visiting! We went on a Monday in the early afternoon and both of them were almost empty with only a few other people.