We're back! Unfortunately, we're back about two hours later than we had hoped, as there was stop-and-go traffic on I-5 (the major north-south interstate in California, which almost never has traffic where we were). I-5's speed limit is 70 mph for cars; in our first three hours we averaged about 45 mph.
The rest stop in the middle of the traffic jam was scarily packed with people. Cars were parked anywhere there was space (dirt shoulder of the offramp, over the curbs on the dirt and lawns, in truck spaces), and each of the four restrooms had lines at least 30 people long.
If you're dying to find out more about I-5, there's an entire Wikipedia page on it, and I've got a few mediocre pictures of the section we were on here.
Considering that we've just been to three family gatherings and one museum (the new de Young) in four days, we're ready to collapse for a bit.