Tri-Met/MAX by fargoman
Portland is a very walkable city however, if you need a cheap alternative to a taxi or shuttle I'd reccomend taking Tri-met. This is the local bus service and also inclueds MAX light-rail system that runs through downtown to several locations in Portland including the Zoo, airport, Convention Center, LLoyd Center (shopping) and other cultural districts. Check out the web-site for info on fares for adults/children/seniors.
