It is actually on a island that has a park and a biosphere as well so yes there is parking. However, if you want to save a few bucks on parking then I recommend parking at the biosphere and walking down to the park as it isn't too far.
I'm not certain if the biosphere charges for parking, but a better idea might be to drive down to the Yellow Line MÄ“tro station at the Universite de Sherbrooke in Longueuil (south of the Island of Montreal), and just take the metro one stop to the Jean Drapeau station which has busses that take you right from the station to La Ronde. I'd also recommend getting the day pass for this, which will cost 9 dollars. However, if Biosphere parking is cheaper, then go for that.