Yes you can let them dry out but you'll have to repot them anyway next year won't you, as the compost will need renewing. It might be better to tip them out and shake the compost off and then bury them in something dry such as dry compost or sand.

It makes no difference whether you keep them in pots as they are, or remove them, clean off all the compost, and store them in dry compost, provided you keep the frost off them and below 50'f. If kept in their pots, do not water.
As has been said, you have to re pot them anyway.

If a prolonged cold snap is forecast, before it arrives carefully dig up the tubers with a fork around the plant about a foot away from the crown then transfer to a pot keeping the soil ball intact. Wrap newspaper layers around the pot to provide insulation if you move the pots to a cold garage if it really gets cold. The soil ball must not get frosted.

In your area you can probably leave them in the ground. If it's just the odd few night of frost a 4" mulch of old leaves or leaf compost put over the dahlia crowns before the first frost arrives is usually good enough to protect it throughout the winter.

The problem with leaving dahlias in open ground is not just frost, but water. More dahlias rot over winter than are destroyed by frost.
Don't use a fork to dig them up. A spade is far better as it cuts through the feeder roots making it easier to lift.
If you must leave the soil ball intact, just make sure there are no slugs, worms or other nasties hanging around in it.

This question was about whether to leave pot grown ones in their pots.

I know, I answered Bendipa who said about leaving them in the ground.

Hi Lizab, I'm in Devon and all my dahlias are in pots which get put in the shed over winter. That's it. I don't dig them up or even repot the following year and they are always fabulous.

Cheers Scrumpy!
There you have it Lizab - why not split them and do both ways, and then you'll know another time which suits your garden best?