I do not think you will have a problem sailing out of Miami. I live in the Cape Canaveral area and hae been concerned about evacuating. Just checked the tracking map on the NOAA website, and as off 1100, they showed Frances making landfall near Jacksonville.
Have a great cruise!
Sitmar Fairwind - June 1985, Sept. 1985, June 1986
Sitmar Fairsky - June 1987
Carnival Fantasy, March 2002
Carnival Fascination - April 2004, October 2005, Dec 2006
Sovereign of the Seas - Sept. 2003, April 2005, Oct. 2005, Sept. 2006
Carnival Sensation - September 2007