It's unlikely they're all dead. I know that many places in California were hit with unusually cold weather. Their survival depends on whether it was cold enough to have frozen their roots in the pots.

The good news is that Fuchias have amazing regenerative capacity. I have had them come back from a few surviving buds on badly split wood--that is usually fatal to most plants. They don't need much--just a few surviving buds and some roots.

I suggest keeping them cool but protected from frost for the rest of the winter (with the understanding that your "winter" is probably over pretty promptly early in the year). Their pots should remain moist enough so the roots don't dry out. You could try trenching them in to protect the roots.

With warmer temperatures, it will eventually become obvious which ones survived and which ones didn't. If you only let them out a day, it's possible most of them will survive.

Have a look at their wood. Dead wood dries out. I suggest not clipping it back until its obvious what is dead and what isn't. They should start regrowing again quickly in mild weather.

In the future, you might want to try trenching their pots. You dig a trench, put the pots in the trench, and bury them. Then mulch the tops. This is just to protect the roots and some buds. Most but not all Fuchsias can stand some frost, and whatever is exposed might get nipped back a bit but in a Sunset zone 14 I would normally expect minimal dieback.

Good luck.

Thank you, atash! I have had these plants for several years and really don't want to lose them. I put them back outside for now as it looks like the frosty weather is over.