"...tsunamis will devastate the coast but that the Golden Gate will prevent them from entering the bay."

I'm snickering here. The Golden Gate is 746 ft above the water, and it's held up by two posts, which are near each end. And what's THAT going to stop or even slow down??? A tsunami entering straight in wouldn't even notice it.

I've lived in Quake Country all my life. One thing I always think about when I think of earthquakes is fires. First, the earthquake hits, severing lots of gas lines. Then all the scared smokers in the area light up to calm their nerves. Funny, huh?

Your situation is worse than practically anything I can imagine:

1) You have no open areas, not even a place to stand that would be free of falling & flying debris, much less pitch a tent.
2) Fire following broken gas mains is probable.
3) Incredibly heavy population density, about 16,000 per sq mile.
4) A lot of the areas on the Bay side are built on fill, which would turn into quicksand in a bad jolt.
5) You're barely above sea level. Vertical land shift up, okay. Major vertical land shift DOWN, you're part of the seabed.
6) There's no real way out. A lot of I-280 and 101 is elevated... for now. Escape on foot, climbing over miles upon miles of debris with other survivors of the, what? 6 million people headed south? You've got what they want? Too bad, you can't protect your head or your back. Fall and break your leg? Ooops.
7) Like you said, there's only one way to go, south. If you get there, you're in Silicon Valley/San Jose, the third-largest city in CA, with another two million people who are in almost as bad a shape as you. Probably no power, no road access for supplies, contaminated water if you can find any, food has disappeared.

Of course, you might luck out and a tsunami would put out the fires.

Sue