Long Tom probably has the best advice for you.
I'm very familiar with the area having been to Dead Shows at Autzen and to Further Fest at Veneta.
Also, some swimming in the McKenzie, but it's cold with a rapid flow.
Cool vibe down there. Granola/hippy situation with lots of cool people and great forests closeby.
I lived in Portland and visited many times, and it's a great place to spend the summer, but don't forget about the GREAT Indian Summer season there. Makes the cold and rainy fall and winter tolerable.
Enjoy.

S