Folks, if you speak some Spanish, here's a website that will be of great interest to you for these hotels:
www.grupoplan.com
This is the company that acutally owns these properties and this website gives more detail and info about the haciendas themselves than I've found anywhere else.
I have been dying to go to some of them now for years, but all my pals are scared off by their remoteness. (That's what attracts me to them in the first place!!!)
That said, I have yet to see anything but positive reviews for any and all of them.