Me and 2 friends want to go to California over the summer. We want to be gone a month and are driving a van. Where should we stop in the middle? We are thinking about going to seattle first, is that a good idea? Is a month long enough or too long?
When it comes to roadtripping, there is no such thing as too long.
That said, you weren't specific enough in your info request. Are you doing a round trip, or will you be flying back from somewhere in Cali? Either way, a month is a reasonable amount of time.
Give us your starting point and ending point, and you'll get plenty of suggestions from myself and other posters.