California is great for road-tripping. Scenic coastal routes such as Highway 1 and Highway 101 are often destinations in themselves, while inland I-5 is the most direct route north and south through the state. However, traffic jams, accidents, mudslides, fires, and snow can affect highways and interstates at any time.
Before heading out on your adventure, check road conditions online at the Calfiornia Department of Transportation (Caltrans, www.dot.ca.gov [1]). Note that mountain passes such as I-80 into Tahoe [2], I-5 at the Grapevine, and the Shasta [3] and Lassen [4] regions may require snow tires and/or chains. In rural areas and in the deserts, gas stations may be few and far between.
Links:
[1] http://www.dot.ca.gov
[2] http://www.moon.com/destinations/california/lake-tahoe-and-the-northern-sierra/lake-tahoe
[3] http://www.moon.com/destinations/california/lake-tahoe-and-the-northern-sierra/mount-shasta
[4] http://www.moon.com/destinations/california/lake-tahoe-and-the-northern-sierra/lassen-volcanic-national-park