It is difficult to generalize how much spending money you will need, as people's lifestyles differ considerably. This includes going out on the weekends, museums, movies, stamps, transportation, personal items, hair cuts, newspapers, etc. Realistically, you should anticipate spending more than you would at home.
Weekends away are fun, but the spending tends to add up.
You may want to bring traveler's cheques and exchange them as you need money. You might also consider having an American Express Card in order to use your checking account. American Express offices allow you to write a personal check in dollers to buy traveler's cheques or pesetas. We do not recommend that you carry large amounts of cash. You must bring the American Express Card with you from the U.S. as you cannot request one once you are in Spain.