I found this on the Fla Dept of Transporation website:
4. What is Florida's Child Restraint Law?
All children 5 years of age or younger must be properly restrained no matter where they are sitting in the vehicle. Children through age 3 must be secured in a separate carrier or a vehicle manufacturer's integrated child safety seat. For children aged 4 through 5 years, a separate carrier, an integrated child safety seat, or a safety belt may be used. (FL Statute 316.613).