We're at the other end of the country altogether, but I quite envy you. San Sebastian is probably the loveliest place I've visited in Spain (so far anyway!) and I'm sure life there will be wonderful. Only potential downsides as far as I could see would be the weather (make sure to bring your brollies and wellies) and I imagine it gets very crowded in July and August as it's a very, very popular holiday destination for better-off Spaniards.
I had wondered before I visited if the Basque language would be an issue in that they might be a bit standoffish with people speaking Spanish, but all the local people we met and spoke to were delightful. Particularly the two ladies we chatted with in a restaurant who had brought their 100 year old mother out for lunch (hope I'm still able to do that if I reach that age - she didn't speak but certainly looked to be enjoying her food) and the old chap who veritably talked the hind leg off the proverbial donkey most of the train journey back to Bilbao!