When? I rented a car in Fort Lauderdale last week, I do this time every year, and had no problems with my UK license.
I think it's only a problem if you get an idiot behind the counter at the rental agency.
But, given that it
is Florida, I'd probably pay up the $5 for the International Licence, rather than play those odds.
Luckily, I'm keeping my WI license current. Also, my sister manages an auto dealership, so I can always get a loaner.