Actually, the port-a-potties do qualify as trailhead amentities. At least, what I have been told by someone who should know. Normally, roadside parking would not qualify for a pass.
Go to the trailhead and park. If you get ticketed, pay the $5. Chances are in the the winter no will up there write tickets. I am forgetful and half the time my pass does not go on the car at Ice House and I am rarely ticketed.
