Welcome to OFF.
If you can let us know, which part of Portland you are in--it will help us, to help you. But in short, you will be mainly limited to the Columbia, the Willamette, and the Clackamas rivers. RC shared a good map, as a fine place to start.
And I always recommend getting a copy of, "Fishing In Oregon", by Maddy Sheehan. Flying Pencil Publications. Most tackle shops, and sporting goods stores, will have a copy. Also the peeps at those shops, can also give you some pointers.