Willamette Park has the best launch facilities, and, IIRC, about $10 to park there for over 5hours. You can also try your luck at Staff Jennings right under the bridge. The launch is rustic (i think its private, but they allow public use), and can be difficult, but parking is free and you'll be right there.
today I saw 4 fish caught there amongst nearly 20 boats
3 by boat
1 by sea lion