This city is placed in the south littoral, 91 kilometres from Florianópolis.
Garopaba is 800 km from south of São Paulo e 1.200 km from south of Rio de Janeiro so I would think the best way to get there from Rio is by flying.
Florianopolis airport is the closest to Garopaba and is about 100 km from Garopaba, to get there By Car/Bus: from Florianopolis, take the BR 101 federal highway, at the Araçatuba junction (at km 272), then the SC-434 state highway. The town is then 14 km away.
Try using the "build your trip" flight comparsion tool here:
Flights To Brazil it will search multiple websites and get you the best price.
Have a fabulous time in Brasil! I hope my reply helps.
Links of interest:
Brazil Transportation Rio De Janiero