Two interesting webpages with information about California freeway and highway signage:
www.kriske.com/highway/signs/signs2.html
www.kriske.com/highway/signs/signs.html
The site has not been updated since '99, but it's still interesting, or a cure for insomnia.
Here's another where you can find more info:
www.cahighways.org/names.html
Enjoy!