I walked that stretch in December last year and some of the albergues were very cold. Ave Fenix and the municipal in Villafranca were not heated (very much), the municipal in Vega de valcarce had a heater which we put into one room to at least be warm there (it also had an open air kitchen, which was coooold! to cook in). All the municipal albergues in Galicia are warm, if stark, in my opinion. I would probably consider getting a warmer sleeping bag, rated to -5 degrees or so.