+1 on the Yosemite reservation.
I had to do so in advance in May in order to get to a Nevada event. No fee for a "pass through" on CA-120, but had to pay the $2 'online' service fee. Even so, when I got to the entry gate there was mass confusion about how I was going to get back several days later. Park entries are good for 7 days. But, they weren't going to let me back because I didn't have a specific reservation to come back. WTF? Fortunately found a sympathetic Ranger who gave me proper entry/exit paperwork.
Patrick Hayes
Fremont CA