They were put in the fridge at day 11 or 12. I'm afraid to take them out (to resume carbonation) because of skunking. Is this valid? I've read the other questions about carbonation/temperature, etc, and I'm hoping they were already carbonated enough that I should just keep them in the fridge. [Its a porter] [brewing at another person's house!] Thanks!!
Take them out of the fridge if you'd like.
Maybe leave one or two in as a "control" to see how the carbonation differs between the 3 groups.
Skunking has nothing to do with entering and then exiting a fridge, and everything to do with light interacting with hopped beer.
It really depends upon how long it was between when you added priming sugar and put them in the fridge. If it were 3 or more days, then you can just leave them there.
The question is really if the yeast had enough time to turn the sugar into CO2. This goes pretty quickly - just a few days if fresh yeast is used, but old yeast will take longer. The remainder of the carbonation time is spent waiting for the gas in the headspace to dissolve into the beer. And then the coolness of the fridge is a benefit - CO2 becomes more soluble with lower temperature so you get better carbonation.