All the towing law summaries I have checked give a flat "No" for tandem (two) trailer towing in Florida. However, federal rules may supercede state laws on interstates and the national highway system, so there may be some leeway there.
Personally I'm against it. Everything goes fairly well when moving smoothly down the highway, but what happens if there is a need to brake or swerve suddenly? Or in strong side winds? A single trailer can jacknife easily enough; two is begging for trouble. Just my opinion...
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL