According to Florida Statute 316.085(1), it is illegal to operate any vehicle while "knowingly and intentionally exposing his or her sexual organs." This law applies to both public and private roads, and it does not matter whether the driver is alone or in the presence of others.
The penalty for driving naked in Florida is up to 60 days in jail and a $500 fine. If you are convicted of driving naked twice within five years, you could be penalized with a year in prison and a $1,000 fine.