Hi! I'm from NYC where public transport is one of the greatest so I didnt like Reunion transport. If you know how to drive I would recomment renting a car. If not, Citalis are buses that run on the east. Carjaune are buses that runs around the whole island. You can google both of these and get some more info. Bonne chance
Carjaunes are the only public means on the island, my boyfriend has been using them a lot and he's had no problem so far. As he's under 26, he only pays 15 euros a month for an unlimited amount of bus journeys.