We visited on a nice Sunday in April with the family. There was already a 20 minute line of cars in late morning, but plenty of parking. It is a bit of greenery and natural area in Miami, so that is a plus.
We thought we would rent kayaks for a trip in the mangroves. This concession is a disaster, and Florida State Parks needs to get a new one when the lease is up.There was a line for kayaks, maybe 20 deep; it didn't look too bad. But the signage is very confusing. Get in the line on the second floor first for the paperwork, then go to the line on the ground level for the equipment. We waited in line for over an hour, and had made little headway, so we walked away. It might be worth the effort on a weekday, but not when there are lines.
Next we hit the swimming beaches. I knew they would be crowded, and they were. But worse was the stench, it smelled like raw sewage. I don't know if it was the water, the restrooms, or just the area. The kids seemed to tolerate it and had fun, but I was anxious to leave.