Don't worry about the Florida law. I've tinted 50 cars at 18-20% all around and have never been stopped because of it. And I've never been cited having it when pulled over for speeding. If you are in the Boca area, Tint & Tunes on Dixie just north of Yamato is great. I know there is a new owner there now, but he does fantastic work. I also put a clear tint on my front windshield to block out the UV. It also keeps the car cooler with using a sun shade.
Don't let the dealer do it. You are better off going to an independent shop.
https://www.bocatintandtunes.com/