I booked it 6 days in advance!!! I think you really can book it right up to the last day, you just won't get your luggag tags/info packet. That's what happened with me. In that case, you just go to baggage claim, grab your bags and then head to the DME checkin desk. It is currently on Side A of MCO but as of next week is moving to Side B!!!! I would call them and get that reservation made. I'm arriving on the 21st also!!!! It's getting closer.