Hi,
You can check by calling National or visiting their website. The Dolphin location is listed as one of their Florida locations.
As for when to book: my advice is book it now and keep checking back to see if the rate goes down. When you book it you lock in the rate but do not have to pay in advance. Then if the rate goes up your rate is locked, but if it goes down just call them and tell them you want to cancel and re-book. Ther is no fee for this.
Bob