The easiest way to get to Florianopolis is by a plane. The international airport (FLN) has connections to many cities in Brazil and also to Buenos Aires. During summer season (Dec-Febuary) there are also direct flights from Santiago de Chile and Montevideo.
In the future there should be direct flights from the USA, Germany and Portugal. Until that happens intercontinental travelers will have to change planes in Rio de Janeiro or Sao Paulo.