We are on the same cruise and heading directly back to the US as well. However, our flight doesn't leave until about 5pm so we have time to kill in Shanghai (we've been previously). Since we don't want to hassle with our luggage, we did sign up for the ship's transfer with a city "tour" to the airport to help pass the time and revisit the Sky Tower. I had previously believed our itinerary worked for visa free, but was having a hard time getting written confirmation from Celebrity. However, just recently I saw in writing, on the Celebrity site, an apparent confirmation of this. They say you must take their tour to be visa free, but I wouldn't think that's the case. That's just them pushing their tours. We were going to take their tour anyway, so it worked out for us. It was just good to see it in writing by Celebrity.