Can't really help you with were to find them in Florida. You could try a google search and see what happens. They are plentiful in the spring and summer in England.
кому Cruzin2 :It depends some nettles seem to have more ZAP too them than others. The fresher they are the more effective they are when applied to the sub. The initial feeling when applied is like being pricked with a load of needles at once to the area they applied to. This feeling tends to build up and last for about 10 minutes then starts to subside to a less painful tingling burning effect .This i find can last from about 30 minutes to an hour depending on how much ZAP the nettles used were. Then subsides to a light tingling itchy feeling that can last as a reminder to my nettling for another 2-3 hours.