Caravan Tours
   Offers all-inclusive, escorted sightseeing tours, eco adventure tours and group vacation packages to Costa Rica, Guatemala, Mexico, Canada and U.S. destinations.
   http://www.caravantours.com/

Green Tortoise Adventure Travel
   Offers bus trips through the United States and south of the border. Includes itineraries, dates, prices, reservations and directions to the office in San Francisco.
   http://www.greentortoise.com/