You sure would! Portland is really great about having 'dog places'--maybe better than I even realized. I went to our City website:
Portland Parks & Recreation :: Park Search Results and it shows you all the off leash areas in the greater Portland area.
So--if you're vacationing in Oregon, and will be in Portland with your pooch-you'll have lots of places to take him/her to play! We've only been to 2 or 3 of them so far, but plan to check more out--some are fenced, and some not, but I'm pretty sure they have water!