We're from the Sunset in SF (and will be going down next Thursday, yay!) and like to leave about 2am, it's completely empty with maybe 20min - 40 min traffic. We notify the hotel that we're going to check in early so the room is usually ready anywhere from 10:30 to noon which gives us a break to have breakfast at Steakhouse 55 around 8:30 and then wander in the parks for a bit.