I'm not sure if it'll help much, but there is a Facebook group (Portland State University Housing, Sublets, and Roommates)...maybe that will get you some leads!
I just sent my decision letter and will be starting this Fall as well! I currently live in Beaverton, right at the border of Beaverton/Portland and am only about 15 mins away from PSU. It's much more affordable to live here. Plus, I'm close to a transit station, so if needed, I could just take the MAX to school.