Unforgettable Road Trip Advice?

I've always loved the California coast. I've been to LA, SF, SD, Monterrey, Santa Barbara, Palm Springs, I love them all. My GF got some time off work, and we are planning a trip from Aug 31 to Sept 6. I thought that taking a road trip through Cali (or even Washington or Oregon), would be a fun way to spend the time. The only thing I need to plan around is that I must be in Las Vegas on the 7-9th for my friend's bachelor party.

If any of you have taken some unforgettable trips on the coast or in the countryside, I would love to hear your suggestions. Thanks!