I think that is a great price - we have done the 3 night and it's really good value in as much it includes all food and soft drinks. You stop in Nassau and
Castaway Cay which is definitely worth the visit.
I would be very surprised if the price came down - the rule of thumb is usually the earlier you book, the cheaper. There are some exceptions for the less well booked cruises such as the Med cruises where offers start coming out, but I have not known this on a Nov Caribbean cruise.
The only thing you could consider is opting to pay in $ as if the rate improves over the coming months, your final balance would effectively come down.
We have cruised twice, once on the 9th Nov, the other the 29th Oct (7 nighter) and both times it coincided with 'Jersey week' when the New Jersey schools are closed for a few INSET days so the cruises were full of NJ-ers, and both sailings were booked out.
Some people will say that the 3 night is not really worth it and to try to go for longer, but we were very unsure about cruising and it was great as a taster. You can always cruise another time for longer if you love it!
Disney cruises can usually be cancelled for a full refund of all monies paid up to 75 days before the cruise, we have cancelled one in the past. I am sure this is still the case, but you may wish to check on the cruise board.
Any other questions, fire away!