So far, I've checked out the Orlando Science Center. Great location, too expensive. $200 for a 5-hour block. It includes parking and admission. May be a possibility for a one-time event.
Leu Gardens - Other plant clubs meet there, why not aquatic? I'm waiting to get the price list.
Panera Bread - They have community meeting rooms at most of their cafes. The price is $50 for one hour. Still a little steep, but a possibility if we have a large enough turnout.
I'm open to other suggestions. The only criteria is that there is parking, it's centrally located, is relatively quiet, open on a weekday evening, and free or little charge.