We did horseback riding on the beach in Grand Cayman 2 years ago. We booked through an independent excursion. The ride was peaceful. It lasted about 2 1/2 hours. If you go be sure to wear a hat, and lots of sunscreen. We were there in early spring and the sun was extremely strong.
One note...if you are used to our healthy, well cared for, and well feed animals, you may have a tough time with the looks of the island horses. I felt sorry for the horses we rode. They were quite scarred and thin. It made the ride less enjoyable. I wanted to get off and walk the horse!
That is so sad, I would have wanted to do that too!
I am wondering if its the same for the mexican riviera horseback tours like in Cabo and PV? If it is, I was debating it, but will probably skip it....it would be too sad.