
Originally Posted by
Midwest Michael
I really can't imagine what other options you'd have, other than a charter bus tour, which you'd already said you weren't interested in. Really, Greyhound is the only national bus option (even they are contracting out to others for some of the trip), and Amtrak is the country's only passenger train service. Any option other than driving would really require you to rent a car, as there aren't many good options to get around Yellowstone without one.
Yellowstone is an amazing place, but it is a long way from any major cities, which does make mass-transit a real big challenge.