If you plan to do a lot of exploring, it’s best to base yourself in the Floripa’s Centro [1]. However, if you just want to flake out, choose accommodations according to the type of beach holiday you’re in the mood for.
If you want plenty of nightlife to go along with your chilled-out days, try the more touristic (and overdeveloped) Praia Brava or dos Ingleses (north coast [2]) or the more attractive rough surf beaches of Joaquina and Mole (east coast [3]). Less crowded are beaches such as Daniela (north coast), whose calm waters make it a favorite for families, and Campeche and Armação (east coast).
For more rustic simplicity and tranquility, check out the traditional Azorean fishing villages of Santo Antônio de Lisboa and Ribeirão da Ilha (west coast [4]). Come summertime, prices are high and reservations are essential. Prices listed below are during low and mid-season.
Links:
[1] http://www.moon.com/destinations/brazil/the-south/santa-catarina/ilha-de-santa-catarina/accommodations/centro
[2] http://www.moon.com/destinations/brazil/the-south/santa-catarina/ilha-de-santa-catarina/accommodations/north-coast
[3] http://www.moon.com/destinations/brazil/the-south/santa-catarina/ilha-de-santa-catarina/accommodations/east-coast
[4] http://www.moon.com/destinations/brazil/the-south/santa-catarina/ilha-de-santa-catarina/beaches/west-coast-beaches