I live in the area, but I haven't ridden it - just sections here and there on assorted rides. It's mostly country roads or all country roads. Funny, I went to the OR state parks site and read the description - it does sound sort of like a bike path.
http://www.oregonstateparks.org/images/pdf/wvsb_map.pdf
Found the above link - All roads 'cept for maybe a path in towns. Nice riding though.
kari