It's mostly a beach vacation destination. Miles of beaches. Known for partying and clubs. Lots of crowds, tourists, particularly from Argentina, in the summer months, and traffic jams. In off season, which your dates are, very quiet. There's some surviving Azorean culture on the island to discover. No guidebook-must-see sights, really, of note. Otherwise, the normal life of a medium sized city.
You could go the couple of hours to Blumenau to see the architecture. Or to the amusement park Beto Carrero World. Or an hour south to charming Praia da Rosa, but again, more beach. Or fly to Iguacu or stay longer in S.P.