The best luck I've had on the Tualatin is just above where it comes into the Willamette. It picks up pretty good a couple hundred yards below the diversion dam. I've only come down from that way, so I'm not sure how it is paddling up that way. Lots of cover, lots of snags, but there are quite a few bass in there. My uncle (who lives on the river there) also claims his wife caught a 4 lb channel cat. When I have seen fish jumping there, they have been squaw fish, but who knows. Boat access would be best if you have that. Good luck!