Hi,
I've been on the Dawn a few times. She's a beautiful ship. We've been on deck 11, and loved it because it was just a walk down the hall to access the spa. And just up one floor for the pool, and buffett. We've also been on deck 9, which was nice and quiet because it has only rooms below and above it. Deck 11 was quiet as well, we never heard any noise from above us.
Aft facing rooms are those across the rear end of the ship. Great for watching the wake, and provide a more expanded view. We always do balconies, just our preference, and usually try to get mid-ship. By being mid-ship, it seems to us to be more convenient, only having to traverse 1/2 the ship to get to the stuff in the front, or the dining room at the aft. If you're in a forward cabin, its quite a hike to the rear, and visa versa. When you get down to brass tack however, we're happy with any room we get, because its on a ship.
As for the passport question, I've heard that you can do closed loop trips (start and end in same port) with valid ID and a birth certificate, but personally I'm not comfortable traveling outside of the country without a passport. I think of my passport as the Royal Flush of ID....trumps all other ID. And, in the very small chance that there is some incident that would require me to have to use an alternate form of transportation back to my starting point, the passport will make that a much smoother trip. But I know that many are quite comfortable doing the cruise without the PP, and just the ID and BC.
You'll have a wonderful time, what ever you decide.