JoeFred, many of those streams have old man-ways that will take you up the drainage to the ridgeline. In the area you mention, Porters Creek and Ramsay Cascades come to mind as having manways.
Be careful in doing so...remember that they had to do a Search & Rescue to find a hiker up on Porter's Moutain last year.
There are also some park rules & regulations relating to off-trail hiking & camping. See page 10 under "Cross Country Camping", and the section showing manways that are closed (I think the Chimney Tops manway is the only one closed right now).