Wow! Do you realize that people from Miami northward along both the east and west coasts are expecting to be hit by Frances? The whole SE U.S. coast can't evacuate! As someone said earlier, make local preparations to secure your home, then get ready to go to a local shelter if and when the time comes.
If you want to go on a long Labor Day weekend trip to, say Kansas(?), leave now and enjoy yourself. You still have time to leave the state. Personally, I think it's too early to be forced to leave - voluntary evacuations along the coast are in order though. "Prepare for the worst, pray for the best."