I would imagine San Miguel, Mahou, Estrella Damne, and the like are the norm in most pubs. I think most local beer is lager.. The Estrella Galecia is supposed to be quite nice and I picked up a few bottles of Cruzcampo and Alahamra on one holiday which is breweed in Grenada I think which were quite nice. Maybe you might find a quirky off licence but I imagine not. Enjoy the craic and don't forget your supply of solpadeine!