If your car isn't reaching temp there's typically only two answers. Coolant or thermostat. The thermostat should restrict the flow so that the engine heats the coolant. Although if there's no coolant too heat, it'll give odd temp gauge readings and a lack of heat because there's no water to heat.
An efficient radiator in Florida.. sorry, the northern folks get much cooler weather, unless you have some radiator we don't have available...it's tough to believe that the rad is doing that to your car.
