By the recommendation of fellow forum member Rook, my wife and I finally drove up Mt Waldo. Turned out to be a nice afternoon so we took the girls out for awhile. Here are some pics. Just thought I would share.
Probably not worth a dedicated trip from Portland just to wheel Waldo. But you could go to All Wheels Offroad in Auburn. It is an off-road park. They ask for a small donation to use the area.