Stay away from Cross Country International. I've heard some really bad things about them.
Equitours has a good reputation.
I recommend the Spotted Horse Ranch in Jackson Hole, WY. One of the most beautiful places on earth, and it's definitely not a nose-to-tail trail riding place.
The price of the package includes 3 gourmet meals a day, beer and wine if you drink alcoholic beverages, and rides that last anywhere from 3 hours to all day.
There's nothing like riding in the Grand Tetons and seeing coyote, moose, elk (we saw a herd of about 200), and antelopes. We didn't see any bear, but we saw their tracks and scat.
Your guides will tailor the ride to your personal expertise. We did a lot of trotting, cantering, and some hand galloping. Helmets use is at your own discretion, and you'll have to take your own as they don't provide any.
I'd love to go back. One of these days, I will. Spotted Horse Ranch :: Guest Ranch Jackson Hole, Wyoming