Need More Info
Welcome aboard the RoadTrip America Forums!
You simply have not given anybody enough information about you or your trip for them to offer anything but the most generic, and therefore useless, advice. Just for starters, they would need to know where you're starting from and going to - "Florida" and "northern California" are awfully big targets; how much time you have; how many of you there are; what your interests are; what planing you've already done. The contributors here are more than happy to help you plan your trip, but this is simply not a one-size-fits-all free trip planning service.
AZBuck is right. We could tell you "I-10 west across the country until you get to I-5 and then go north", but that probably wouldn't help you. What if you're not near I-10? What if the part of Northern California that you want to go to, is located on the eastern edge of the state (instead of the center where I-5 runs)?
What do you want to do on your trip? Is a speed run where you just want to get to this side of the country before you start to see things, or is a leisurely trip across? Both types of trips are good, but we can't help you plan.
Take out a good USA map or road atlas, and see what hits you. Then when you have an idea or three, come on back and we'll give you a hand trying to connect the dots.
As well as all the above, it is vital for members here to know what the purpose of the trip is. Advice would be very different for a relocation, than it would be for a sightseeing trip; for a preference for nature, than preference for theme parks; for a one way trip, or a return trip.
Without your input, no one can help you.