I-10 is a perfectly good corridor for transiting CA To FL...there is only one real grade and that's a short one just east of Indio CA and then a long pull just east of Benton AZ, somewhere in the 3% range. Other issues as far as campgrounds or support for your trip can be sporadic but available. It can be hilly with long stretches between stops but you'll not be alone, although the traffic pressure is light it's a major truck route. Once you hit San Antonio TX it flattens out all the way to the FL panhandle where you'll get a few rollers.