If you have booked a package (room+tickets, with or without dining), you can cancel anytime before 45 days from arrival (when your balance is due) without penalty. After that, the penalty is $200. Or, you can postpone your trip to sometime in the future and have the funds applied.
If you booked a room-only reservation (one-night's stay deposit), you can cancel up to 6 days in advance with no penalty.