I'm noticing that my first year trees are drying out too fast in their containers.  Is it too late in the season to move them to a SWC?  I'm in Southern California so my season will likely last well into November.

Can't you move them to shadier areas and give them more water? When I transplant, I put them in a shadier spot for 2 weeks to acclimatize to the sun/heat.

I just up potted my 20 first year trees from 3 gal to 7 gal pots. they were all pretty root bound and some were drying out very quickly.

Go for it.  I just moved 4 of mine from a 1 gallon pot to a 5 gallon SIP.  You have plenty of time!

Don't disturb the roots while doing it.

Thank you for all the replies!  For a SWC, how do you all go about adding fertilizer.  Do you mix in or top dress?  

I would go for it!  I am not too sure about fertilizer, though. I usually only add fertilizer to my figs in the early spring.I have not issues replanting any figs, as long as you minimize damage or disruption to the roots when transplanting (unless, or course the plant is dormant).

Best of luck with the move.

I add some Osmocote slow release fertilizer pellets in the potting mix.
As mentioned, you want to ensure the entire root ball will come out of the pot in one piece so the roots are not disturbed.