I recommend travelling in Spain in Spring, its alot greener, there are very cheap ferries to Bilbao, no one is patrolling the no camping zones by the beaches and the forest fire risk is much lower. And less tourists in the hotspots. When you have Spanish sun a few showers (or night frosts) are fine, stuff dries out really fast in a sunny period.
Late summer can be uncomfortably hot.
The coast of Galicia is the most interesting bit, inland its comparable to rural England with vastly less motor traffic. Stone walls with moss on top, oakwoods to camp in, shared with long horned cattle with cowbells.
I did Bilbao, Oviedo, Santiago, Elvas, Monchique, Cape St. Vincent in 2007, over 4 Months. Camped wild all the way. No problems with landowners or dogs. Windfall oranges on the verges for breakfast.