What Driftwood said ^^^! Madrid has a great 'foodies' market, which you can get amongst prior to bar-hopping and grazing some more tapas late into the night... Some great Gin bars in Madrid too ;-) Even if you plan to stay in one spot on the coast, conditions change rapidly so a car is extremely useful. Water and air temps may be surprisingly chilly if you happen to be travelling down from France. Unsurprisingly, there are a few surf shops in Mundaka and whilst it has been a long time since I was there, there were plenty of used boards about.... Also, whilst I've not seen the boards in person, I've heard good things about 'Peta Surfboards' if you are thinking custom.