You wont have any problem finding them in South Florida especially in the May/June time frame.
Most will fall into the 10# and under size however. Taken on lighter tackle as most are in S. Florida even a 10 pounder can be challenging. That time of year there will as a rule be massive expanses of floating sargassum weeds on the surface of the water. That attracts the bait which attracts the larger preditors. So the drill is to troll along the edges untill a Mahi is hooked and brought to the boat. As a rule others will be attempting to steal his prize and can be kept at the boat by chumming with cut bait and caught on spinning rods. The larger ones as a rule are caught while trolling in the open ocean, which can like trolling for any species become very boring.
I would suggest the Keys, since you can combine the trip to include Mahi as well as the better tasting reef species on the same day.
