San Diego thru Laguna Hills to Fresno, Ca.

I would take Hwy 15 north to Hwy 58 and then head west to Hwy 99 and north to Fresno. Much less stressful than going through the Los Angeles basin which starts to get ugly as far south as Capistrano, or to have to go over the grapevine on I-5.

There is a very nice RV park at the glider airport in Tehachapi which makes a good stopping point along this route.