Hopefully someone more knowledgeable than me will answer, but I think you can prune them without worry. Worst case scenario (if they turn out to be the sort that blooms on old wood), you will lose a season of bloom.

Good luck!

I doubt they are as far gone as you seem to think :-) Even in CA, hydrangeas look pretty funky at this time of year - for your location, it's as close to dormancy as they are inclined to get and bare stems with mostly brown or yellowed leaves are to be expected (they are not evergreen plants and winter is when they drop foliage and rest). My sister grows a lot of hydrangeas in her shady Laguna Beach garden and they all look pretty ragged at this time of year.

I'd also hesitate to endorse any pruning. Bigleaf hydrangeas (Hydrangea macrophylla) seem to be the species most often grown in CA and the evidence of pink flowers would seem to confirm that (Annabelle's have white flowers). Bigleaf hydrangeas bloom on old growth and pruning is generally not required or recommended unless the plants are grossly overgrown. If these are "smallish" plants as you indicate, why is there a need to prune? You can certainly remove any old, spent flowerheads and any deadwood (bare stems with no buds and with a light, grayish-brown coloring) but otherwise no further pruning is necessary.

Mulch them well with a thick layer of compost (avoid piling against the stems) and make sure they have adequate moisture. I wouldn't do anything else until you see how well they respond to spring and warmer temperatures. They are very probably just fine.

I appreciate the info. It is helpful. How do I remove deadwood? Do I just cut it off? Also, I looked at them today and was surprised to see many more new leaves. It does seem like they will be fine with some TLC!

Yes, just prune it out at the ground or where it emerges from any live growth. Clean, flush cuts - don't leave stubs.

You may want to wait pruning until the plant has properly leafed out before pruning. Some dead-looking stems may be not be dead or the bottom parts may be alive. Always hard to tell for sure unless you resort to pruning at 1" intervals looking for green on the stem.

I always leave this chore to the time of the year when I can see the broccoli-like florets developing on the plants. If the stem has not leafed out by then then I prune it. In the north, this can be as late as June-ish. Here it is around May, but it varies a lot. In Z10, it will probably be a little earlier than here (Z8).

Since zone 10 hydrangeas barely even enter dormancy, I doubt one needs to wait until May - all my hydrangeas have formed leaf buds by now and will be in full leaf easily by May. And it is very easy to see what is live wood compared to dead. Deadwood with any woody plant can be removed at any time it is noticed.