I moved to SFL a couple of years ago and have been thinking of buying a rifle for far longer...finally bought a preban AR -15 and have been looking for ranges.
Here's what I've found:
Sebastian (near Vero Beach)
http://bcc1.co.indian-river.fl.us/de..._range/gun.htm
Sunrise (Broward)
http://www.co.broward.fl.us/parks/pri01600.htm
These are the only two I was able to find - & haven't been to either yet.
Good luck - and pls post if you find anything else.