What bikes have you got? Two up? Or ...

Start off doing the Pyrenees. You can take a week dipping in and out of Andorra and vicinity. Tight, small, narrow roads through stunning mountain vistas. There are off road rental shops in/around Andorra and some nice trails to explore there. You can rent Trials bikes and take a class too.

I've done two tours of Spain. No camping, as cities are some of the best things to see there and best places to be. Discover Tapas bars to save money and find where locals eat for Lunch. (Plata del dia or somesuch)

In the country side you can camp I guess, but not so much in cities? Dunno?

I crisscrossed Spain in my two months, all the way to Portugal. Too many good roads and places to list here. I liked in interior best and the Pyrenees, going back and forth on the many passes between France and Spain. It's all a hoot!

Get a good guide book and pick out what suits you. The touristy beach areas (Costa del Steam Hammer Pile Driver) are crowded and expensive but a few unspoiled ones ... if you can find them. They've overbuilt badly, many have gone bust.

My favorite thing in Spain was Alhambra Castle in Granada. Stunning.
The small to medium sized INLAND towns were my favs, stick to small roads like around Ronda. Small mountain roads are most fun and get off the tourist circuit.

If you're race fans, maybe catch a MotoGP. If you time it right and if you can handle that madness. 2 or 3 world class race tracks in Spain. The Spanish are MAD for bike racing and bikes ... never try to outrun Spanish cops on the motorways. They love a chase ... but have NO sense of humor.

For the big cities leave the bike somewhere (Hotel, Campground?) Use public transport. I avoided Madrid but did do Barcelona ... good without the bike and a lot to take in.

More adventure? Go South to Tarifa and take the boat over to Cueta, Morocco for a day or two. Leave bike in Spain. Another world ... but frankly I preferred the "Moorish" areas in the Spanish towns. Narrow cobblestone streets, little shops and Cafe's. Wonderful atmosphere. Many Spanish cities have these small Moorish Arab "ghettos" sections, which are fantastic to walk through. Just like Morocco without all the hassle.

Yo have really near Bilbao and Santander

Virtus offroad

This people have guided tours, but they are more orientated to enduro, if you feel happy with that, they are your best option.

On the other hand, I don't mind to show you some nice routes, but I don't have bikes for rent.