Well hello >.<
I live in portland, and most of the driving (the fun driving that is) I have done at Browns Camp which is towards the coast and the cascades or at least in that direction.
I am somewhat of a novice though, and with my truck in somewhat of a limping state, I will not be going any time soon. I know that it (browns camp) is closed for the winter, as it is mainly an ATV, dirtbike place with a few fit-a-car-down-there trails, although I must admit, it is a blast. Going when or after it has rained cuts down on the dust and add's to the fun/difficulty.
I would recommend taking a extra gas tank, a GPS, or some flagging tape; last time I went someone had gotten lost and eaten up all of their gas on the back of a ridge way out of the way, and with no cell reception, you are pretty much hosed.
Best of luck, I'll check back to see if anyone else posts, and I'll repost when my truck is running tip top again.
-Elliott