Pete,
By way of practice, I highly recommend car camping with whoever you would be evacuating with (wife, children, pets?). Or without them if they aren't eager.
You'll learn what you need to have in the car to survive comfortably for some number of days. You can practice different routes out of town.
Leaving home on a Friday of a holiday weekend and imagining that times a factor of 10 would be some approximation of what you'd have to look forward to in a mass evacuation.
Practice makes perfect. I've been car camping in this region for twenty years so have the gear (have camped in overnight temps in the teens), know what fits in my vehicle, know the campgrounds and routes to get to them.
By the way, do you keep your vehicle in a garage? Occurs to me that in earthquake country it could be wise to keep the evac vehicle outside of the garage.
Also, if I were evacuating among the things that would be going with me are mountain bikes on my hitch rack and a bike trailer and Burley Travoy on the roof (Yakima Loadwarrior).
Burley Travoy - I got this for grocery shopping (works as a bike trailer or hand truck) and it is so light and compact that it is now part of my road trip gear.
http://www.burley.com/home/bur/page_416/travoy.html.