If something unusual happened and you needed to return to the US by plane, you would be very delayed while the consulate works through the bureaucaracy to get you a passport. I'm not even sure that is still an option and if it is, much, much better to just bite the bullet and get the passport. You will want to start now to ensure you have enough time to get it or you will have to go to a location where they can do a rush passport which will cost you more money.

Most of the travel sites will have cruise deals, just compare. September is a great time to do a cruise because it's off season and the rates are about as low as you will get. Cruises are a very inexpensive way to vacation as long as you don't gamble or drink. Also, you can save money by waiting until you get off the boat to book an excursion. They offers the same excursions on the pier for less money. On the other hand, if you book through the cruise, they take care of everything and guarantee you make it back to the boat. Never been an issue for us, but sometimes peace of mind is worth a few extra bucks.