Hi topherstephens! I'm so happy you've found the message board to be useful in planning your upcoming trip.
I honestly have no experience with camping in Spain (only in the USA), but you might visit
www.VayaCamping.net (English version available) to see the few campsites available near San Sebastian. Just so you know, San Sebastian is in the province of GUIPUZCOA -- this will help you narrow down your search - they have a clickable map on the site.
I too would be interested to know if anyone has camped on Spain's northern regions.
Good luck and have fun! Saludos, MadridMan
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