I know there's a smallish casino in San Sebastian, when I was there a couple of years ago they were advertising poker. It seemed to run at a set time, but I didn't really ask details since I was backpacking and had no wardrobe with me to speak of that would have been appropriate for a european casino.
They have a website, though it doesn't seem to be too informative:
http://www.casinokursaal.com/en/index.php
San Sebastian itself is one of the most beautiful cities in Spain, and the food is out of this world.