You only gave western NC as your starting point so I used Asheville as a starting point. Yahoo maps gave the following route from there out to San Diego. Here is the link that they gave me. http://maps.yahoo.com/#mvt=m&lat=33.31811&lon=-99.78153&zoom=6&q1=Asheville%2C%20NC&q2=san%20dieg o%2C%20CA
This uses I-20 and I-10 for most of the route. It looks to be the shortest. Wishing you safe travels.