Waldo and SweetAss - You might notice that this thread was posted on the PCT forum - not the AT. Southbound hiking is a very different experience.
This is probably not a good year to go southbound - largely because of the high snow levels this year in Washington and the damage that was done to the PCT there in the flooding last fall. The Forest Service will probably reroute the PCT in some places where the trail was washed away and the bridges are gone. Some of those rivers you really don’t want to cross without a bridge. They won’t even know what parts of the trail are passable until July. They won’t begin trailwork until August - if then.
As to water - the rainy season in southern California is February-March. So it will probably be dry when you reach the desert if you do a SB hike. There won’t be water caches - those are an April-May phenomenon.
It is much harder to do a southbound hike on the PCT than on the AT. Far fewer people finish the trail going south than going north. I think that in part that is psychological - southern California in the fall lacks the splendor of the Cascades in autumn. The thing that made S.Cal interesting was seeing it in spring, with all the desert wildflowers. I think it would be easy to lose motivation while winding through the endless hills. But a few do it.
Try posting on PCT-L and see if you get any responses. I can’t think of any southbounders there, but there may be a few.