The ACA Southern Tier route goes from Phoenix to San Diego. From there, it is a couple days up to LA, depending on where in LA you are going.

You can see the route from Tempe to San Diego on this page: http://www.adventurecycling.org/rout...southern-tier/

I've ridden the route from LA to Phoenix in the opposite direction. It wasn't very interesting, but got there without incident.