Trey, if you are going to be in Spain in July and are looking for festivals/parties, one of the most well known ones in the USA is San Fermín in Pamplona. The celebration is a week long, but the biggest party is on July 7th. San Fermín is most known for its "Running of the Bulls". IMO it´s one of the most grotesque displays of public excessiveness....but I maintain that it must be experienced once in your life! :-)

If your Spanish is up to par, try checking out Fiestas Atope website. It has a chronological listing of all the major festivals in Spain.

Happy travels!