I want to have gender reveal in a about three weeks. How long would it take to get approved and how much would it cost for at least a hour and a half

Contact the city of Jacksonville parks and rec department.

I guess it would depend on how much your revealing

I don't think it would cost much for only 90 min, but you should contact parks and rec as soon as possible in case there is a conflicting event already scheduled. Reserve it as early as possible.

My buddy did veg fest there..i think it was 1500 for the park for a day