especially appreciate your suggestion that those wanting to go horseback riding book through their casa--and even then, I would suggest that they check out the horses first and REFUSE to ride those who appear ill-cared-for.
What does an ill cared for horse look like? Inform yourself before you arrive.
ALL the horses I saw in Vinales looked underfed, with ribs and hip bones showing on many, and the rest unhealthily underweight, including those for tourists to ride, most for the "guides" or other locals (except a few cowboys who compete in rodeos),, and any pulling work carts.
These guys who run the horseback riding "concessions" are NOT feeding these horses grain, which the horses need to stay healthy. (I have worked professionally with horses and do know about adequate rations for them.) There probably isn't horse feed grain even to be had on the island, even for a price, except for the Olympic Equestrian Team horses in Havana and those in the government breeding and sale program. The horses in Vinales and elsewhere in the Cuban countryside are only being pegged out to eat grass, which does not provide enough nourishment, particularly for the amount of work they do.
Booking through a casa doesn't change any of the above.

