Basically, it's still WAY to early to tell what kind of impact Isabel will have on the Bahamas or the US, but she could be somewhere near the Bahamas by early to the middle of next week. If Isabel gets close enough to the Bahamas, it could definitely impact cruising, because the swells will be very large since it is a very intense hurricane. However, unless Isabel heads directly towards the coast of Florida, the worst thing that would happen would be an itenerary change in the 3/4 day cruise, maybe changing to ports like Key West or Cozumel (if that's not too far away for a short cruise), areas away from Isabel's impact.