Hola Amigos!
I first visited Spain in 1997 when I spent a semester in Sevilla. It's a great place to live; full of great people who know how to relax and enjoy life; great food, especially the many tapas to choose from at the bars, and the weather is fantastic! I recommend spending time in Barrio de Santa Cruz and searching out La Carbonaria, an old bar that flows with the spirit of Flamenco and the Duende of the Gypsy influence. You can usually hear some great traditional music here which carries on late into the evening.
I moved to Valencia in Sept. 1999 to teach English and spent 8 months there. Definately go to Plaza de la Virgin on the weekends for the outdoor market and hit the many bars on calle Caballeros. There are many outdoor markets throughout the city, all of which occur on different days. Tuesdays there is one close to the train station. Also go to Mercado Central for the freshest seafood, produce and deli items that Valencia has to offer.