Bilbao – Gorliz – it’s at the end of the metro line.
Never used this campsite, but Gorliz/Plentzia are nice places.
http://www.campinggorliz.com/es/home/1.html
Zarautz – between Bilbao and San Sebastian.
I’ve used this one, very nice location, smart town too.
http://www.grancampingzarautz.com/
Hondarribia – just past San Sebastian on the French border. Linked to San Sebastian by train and bus.
http://www.campingfarodehiguer.es/es/ Nice campsite, little bit of a walk into town, (there’s a shortcut/steep staircase straight down the hillside).
Again, nice town, good beach. The base for http://www.basquemtb.com
when you coming over?
Also – Mundaka, near Gernika has a good campsite, apparently it has the biggest left-break in the world, whatever that means.
Mundaka is small and quiet, but linked by train to Gernika and Bermeo which are livelier.
http://www.campingportuondo.com/en/