Yes, there are a lot of Northeasterners down in Florida, that might have some fond memories of Mitt in MA, but not nearly enough to make a difference. I don't seem to remember Giuliani doing well down there four years ago.
Current polling shows Newt with nearly three times the strength of Romney :
http://www.politico.com/2012-election/floridaAnd that's with Cain still getting a couple of points less than Mitt. I predict that the lion's share of his support goes to Newt, with extremely little of it to Romney.