I was having a joke with you. Spain has so much to offer. You can drive down the Mediterranean motorway from Barcelona to say South of Murcia and then cut across country to Portugal and back up again along the Atlantic coast of Portugal. Rather than tell you to do this or that i would say in 3 weeks you would have a lot of fun just going where you feel like. The motorways are great there as they are virtually free of trucks etc due to the tolls you have to pay.
I suggest that you join a site that gives cashback, such as Quidco.co.uk, and use one of its related booking sites, such as hotels.com, and you could save upto 25% on your trip. Tripadvisor is pretty good for visit advise, but I would suggest Segovia, Valencia, Madrid, Seville, Grenada & Cordoba are musts in Spain