Yep, and many business are named after it. Just google PDX and you'll find a mess of 'em.

Portland has more knicknames than just about any city I know:
PDX: airport designation
Stumptown: When the town was new, they cut down trees to make way for houses and such, but left the stumps
Rose City: weather's great for roses
Rip City: harder one to explain, but as a Golden State Warriors fan from back when they won their first championship, I know the story. A guy named Jim Barnett was traded to the Trailblazers, and hit a long and wild shot. The announcer yelled out "Rip city!", somehow it stuck

There are more, but those are the common ones.