I've never been to San Sebastian, though we are going there this summer. I have been to the Algarve, and it was fantastic. We stayed in Salema at Rick Steve's favorite place, the A Mare
www.algarve.co.uk. It was wonderful, with a great view, and reasonably priced. The tip of the Sagres peninsula is one of the most beautiful places on earth. The beach in Salema is really nice, and not crowded (we were there at the end of June, 2 weekdays). The water is warm. Lots of surfing if you drive to Portugal's west coast. Portugal is really beautiful--but it's not Spain. Other parts of Portugal--Lisbon area, and northern Portugal--are even more interesting. Buy some ceramics. Portugal is a lot like California, except with ancient culture, and not at all as built up. Watch out for truly insane drivers.