You may want to double check with Carnival (1-800 CARNIVAL) to make sure. I called Carnival today and they said it leaves out of Red Hook (Brooklyn). You don't want to show up at the wrong pier especially on a Friday (11/13/09) for a 5:00 pm departure.
Which airport are you flying into? (Newark, LaGuadia or JFK). The reason I mention this is because arrival times, carriers, and airfares between the three may vary.