I've not ridden in Spain, but when I've driven a car there I've found the emptiest, bendy roads with tarmac so beautiful it's enough to make grown man weep. People write epic poetry about biking in the Pyrenees and the Picos. I'd say simply not to spend too much time at the coasts (which are busy), and the roads should be awesome. It's place I'd love to take the bike. There's a ferry to Bilbao from Rosslare, if that helps.
Don't be too rattled by the cameras. It's just better to realise that things have changed and to be aware of those places where you need to careful, than end up with a collection of fines after you get home. I was in Germany, Belgium, France and Luxembourg for a week last year, had great fun on the roads, and got no fines.