text:  Andres Pulido gets around the center of Medellin on a wheelchair that has a third wheel in front. He's part of a group of nine tourists who are using similar vehicles. They look like tricycles and can reach speeds of up to 20 miles per hour. After driving for about 10 minutes on the sidewalks and streets, the group stops at a broad square with smooth concrete tiles that is surrounded by bamboo trees and tall lampposts.