RE: Double Westy
Let me expand on Jim's response a little, based on several trips in the last
couple of years traveling with another Westy (and recently with a 23 ft RV)
In Washington State Parks, even when the sign says 'Second vehicle $5' you
can not have a second vehicle with built in sleeping quarters, period.  It's
actually written into state law in Washington.  And based on experience very
tightly enforced.
According to discussions with park rangers in Oregon, the same applies and
again is 'the law'. BUT, you can find exceptions in Oregon State parks, as
Jim pointed out. But at parks like Nehalem Bay, strictly enforced. But
apparently not as rigidly enforced in other parts of Oregon..
In California State parks you CAN double up, no problem, but usually a 2nd
vehicle fee is attached.  But if there is room, no problem doubling up.
In all the Federal campgrounds I've been in (National Parks, Forest Service,
BLM, Bureau of Reclamation, etc) they have allowed you to double up.  And I
ran into a couple on this last trip that had no second vehicle fee.
And most locally run county campgrounds I've been allowed to double up,
usually with a second vehicle fee.