We went on a horse ride tour to El Limon with Santi as advised here by one of the reviewers.
First, the lady at the desk didn't speak English, Spanish only - we felt it's strange taking into account that this company is so popular with tourists. She started giving us different prices in pesos for foot or horse tours, including lunch. We didn't want lunch and asked if she got price list in English. She got one - and the price for a horse ride was 750 pesos per person (without lunch, but tour, guide, and horse included as it was written). We confirmed we wanted exactly this kind of tour and paid. It was around 3 pm, and the guide was available right away (a phone call away and was at Santi in 5 minutes). Before he came, the lady started explaining to us we need to pay additional money to the guide, showing us 300 on calculator (meaning 300 pesos for guide). Since she spoke Spanish only, we couldn't really understand if guide is included in the tour or not. The guide was a Dominican guy, around 15-16 years old (hard to judge, but he looked more like a boy than a man). He didn't speak English, either, but on our way he tried to entertain us, showing different kinds of fruits and being overall very friendly and helpful. He also seemed knowledgeable of horses, and we felt very comfortable on horses with him along. He also explained to us as good as he could that he is not paid by the company, and all money he got for doing these trips are from tourists whom he is guiding to the waterfall. At the end of our trip we gave him 500 pesos, and he looked not very pleased - as though he expected at least 1000 p. We felt pretty strange after all - what have we paid for? The entrance fee for El Limon is 50 pesos per person, then for what we paid 700 pesos per person at Santi? For them, finding us a horse with a guide, if the guide is not paid by Santi? That's it?
As for the waterfall, it's nice and refreshing, and views are spectacular. Keep in mind, though, it's pretty far away, and trip is demanding. After a 1-hour ride one way we got off our horses and needed to walk down to the waterfall (50 meters drop) for another 15 minutes. The trip back to the horses, uphill all the way for another 20 minutes, was very tough.