A bit off trek but on the way from the Franciscan Missions towards El Tajin, and totally worth it. It is also really popular. I took more pictures here than ANY other place in Mexico but it also took effort to have nobody in the frame, especially with Mexican kids splashing in the water. If you want to get close to the El Waterfall you either take off your shoes, prepare to get wet or buy booties in the shops before you enter the gardens.
If you try to imagine this is an ancient ruin with unknown origin and you would think it's a mysterious place ranking among the Mayan ruins. Alas it is not. Somehow inspired by Dalí and you can imagine what it is like. Art overgrown by jungle. In another example, have you been to Siem Reap and how the "Tomb Raider" temple gets a lot of attention and is very photogenic? So then you should understand that every corner he is just asking for a picture.
Edward James created a very unique place and I believe this should be part of the world heritage. I think it also reaches beyond what you see here as the park is apparently 80 acres with a sign stopping you to explore the rest of the garden because there is no security. The park is in the forest and wild animals could probably mame you (leopards?).
Is the park actually complete to the artist's intention? I didn't have a guide, incidentally there was a group of foreigners with a guide so they are available. I don't think I need a guide to experience the place but that would be something to ask. The The House on Three Floors Which Will in Fact Have Five or Four or Six is basically Solivagant's unfinished house in Sherwood Forest now overgrown with ferns, moss and ivy. Staircase to Heaven is also just that, staircase going up in an unfinished house. This only works in the setting here with the slightest decoration because if you have it somewhere else it's just "unfinished house waiting to be demolished" by artists called Mexican Builders.
Nevertheless you can see a lot here. It was rainy which is probably common and steps can be slippery. With an entrance of 100 pesos you are also looking at more than the usual ticket price. There are lots of hotels in the area to park and walk over (or taxi if you find the hill a bit too much but the last section is actually annoying to walk so if the taxi drops you off at the garden entrance you save some muddy shoe cleaning and miss out on trinket shopping).
Lastly I think this place will start to need a lot of maintenance in this setting but for now it seems almost original.