Woohoo, Chickie - did you ever open a rat's nest!
Everyone has their own personal opinions about dogs and everyone has had their own best dog. I have a Boston Terrier and a Golden/Shepherd cross. They are both fabulous with the birds (ducks and chickens) and I leave the entire manegerie out in the yard by themselves all the time. The golden took to the chickens immediately but could care less about the ducks. But, the shepherd in her comes out and she always wants to herd them! The chickens can't wander 5 steps out of the circle or she's herding them back in. Drives the birds nuts. But that is just her nature. I would never, ever recommend all golden's based on her nature.
I think your best bet is to find a breed that is specifically bred for livestock protection. My first recommendation would be the Great Pyrannese, although a good point was raised about the Florida heat. They have extremely thick coats and are huge dogs. They are specifically bred for bonding to certain animals or people and protecting them though. The downside is that if you get a pyranese pup and it bonds with the chickens, it will be very protective of them, even toward friends and "friendly" animals. They are used extensively at the US Sheep experiment station with the flocks, but they are adamant about not allowing them to bond with a human, because then they will not guard the sheep properly.
For you want, that's probably the best training though. Not a family pet, a guard dog.
I would not recommend any form of lab or retreiver (even though I have one). Yes, they are sweet tempered and I don't believe most would ever go on a killing spree, but they are bred as bird dogs and will constantly be picking up the birds to "retreive" to you.
Just a few ideas. I hope this helps. It's a tough decision.
(BTW - My own opinion is that getting a dog as a guard dog for your chickens is a very valid purpose. Not every dog was meant to be a lap pet and some people do certain breeds a disservice by not allowing them to do what they were bred for.)