We were there last week of October. Stayed in the four bedroom five bath presidential penthouse, on the rooftop, which was pretty cool.
It will be hot in September, but at least it's not a humid heat. We were there in October during the grand fishing tournament and the town was lively but it was not annoyingly busy.
It is hurricane season, and you take a chance indeed.
Remember there is no swimmable beach. Resort is beautiful but if you stay in the non VIP building, where the studios, one and two bedrooms are, you may be looking at a crane since they are still building next door.