Portland is going to be wet until July 4th. You just missed a mystifying stint of bone cold dry ass weather. Brooklyn Street Skatespot is a great DIY spot (SE 16th + Brooklyn). Commonwealth (SE 20th + Hawthorne) is a rad indoor park but sessions is pricey. DOS bowl and Unheard ramp if you know someone with a key. Get on food stamps while you're here, it's too easy.
Also, there's some small metal ledges, a jersey, and a big bump right next to the train station. Bomb the west hills from Washington Park aka ZOOBOMB. Zoobomb is really a bike thing but the hill is universally known as such. Matter of fact go to Zoobomb on a Sunday night with the bike weirdos and you will have fun.
Best advice is to wait for summer unless you aren't expecting to skate every day you're here.