If you buy a car in CA and take it out of state to register it (ie. never register it in CA at all ) and get a note notarized in Nevada for example, then you do NOT have to pay CA sales tax.

I did this last year.
Bought a FEH in Calif. and drove it out of state the same day, and got a paper notarized at a Las Vegas Casino saying I took delivery in Nevada. The paper went back to the CA dealer, so he/she has proof that it was an "out of state sale" when the CA tax collector comes calling.

About 3 months later I got a refund check for $15 too with a note saying a CA motor vehicle fee was included in the purchase price, but since I registered out of state, I was not required to pay that!

I did have to pay CO sales tax, but that was 1.5% less for me!

-John