Walking by and enjoying the strolling. Romanic architecture, Picasso's first steps in art, beaches to get suntanned (as far as the weather allows you) good value in shopping, good food, sports, and lovely people.
Quick Tips: Try to learn basic words in Spanish because, although people study English in school, they don't speak it. Everybody will be willing to help you anyway.
Best Way To Get Around: Public buses are cheap and they can get you anywhere in town. The old town is closed to traffic though. It's really small so it's a good chance to get lost in the streets, and believe me, you will. I've been there lots of times and I can get lost very easily there.