We spent such a short amount of time in Spain that we do not have a lot to say other than our two trips to castles and rock climbing. We did not spend a lot of time researching the area before we went, but figured that since they spoke Spanish, it would not be a lot of trouble.
Of course, there are people in Spain who speak Spanish, however in the areas we visited: Barcelona, Valencia, and Calpe, they speak Catalan which is similar, but not the same thing.
There are a few things we would recommend while in Spain, and that is if you are on the coast, you should try the seafood tapas and the seafood paella. Tapas are similar to appetizers, but you can go to the bar in a restaurant to order a few that they specialize in and then go to the next bar to have a few more. Likewise, many restaurants allow you to order them with your regular meal in the dining area. The steamed mussels were absolutely wonderful. We also tried a cuttle fish tapas and that was good, too.
Our favorite was the seafood paella and the vegetable paella. The rice there is not like ours here and they must use a lot of butter or oil to get it so good. Paella is for two people or more. It comes in a large pan. The rice is cooked and seasoned and placed in the pan with steamed, grilled, or cooked vegetables and meats. We can not find the equivalent here in terms of quality and taste.
If in Barcelona, you might enjoy going to Gaudi's castle which is not done yet, but is very unique in its architecture. Gaudi also built an estate that was later turned into a public park and a school. My friend who has been there recommends these.
If you have the chance, dip your feet into the Mediterranean. It is wonderful!