It's such a wonderful Island...I live there, but right now I'm an exchange student here in USA.
There are attractions for all kinds of tastes. Great beaches. Good to surf, and play a lot of summer sports. Also one of the most famous place to sendboard. Very fun. It's very close to snowboard.
The nights are perfect!!! A lot of night clubs, Bars, show houses, movies, theatres.
Sao luis is also a historical city. Downtown you can see old French and Portuguese buildings, and all kind of artcraft.