The Florida Division of Emergency Mgmt. has a hurricane evacuation map available through their public mapping tool at:

http://public.mapping.floridadisaster.org/PublicMap/index.htm

You will have to zoom pretty close in on an area of interest to be able to check the "Evacuation Zone" map. You can also see storm surge maps for the coastal zones as well.

For instance, the Merritt Island area is rated, in parts, at Cat 5 storm surge, but the entire area is rated as evacuation for a Cat 1 storm. It's entirely up to the person there to make the final decision, but knowing that area at least somewhat well, I'd be inland if a storm was threatening - at least in Cocoa or Melbourne or someplace off of the islands.

The map is a pretty useful tool for those of you in Florida; if you get a chance, check it out. It requires you to install a plug-in from Autodesk, but it's not spyware or anything (for those worried about that).