MEET AMERICA’S new travelers: seniors riding buses to Canada to buy prescription drugs at a discount. These medical tourists come from a country with access to the best health care in the world. A bevy of cures and preventive prescriptions have freed many from hospital beds and deteriorating illnesses but burdened pill-takers with exorbitant bills at the pharmacy window. By journeying to Canada, or Mexico for many Californians, consumers can fill their medicine chests with the same drugs for 30 to 50 percent less money. For anyone needing prescription drugs, it’s an infuriating situation. Drive a few miles across the border, and an identical pill can be purchased at a fraction of the U.S. price.