Wow, great stuff. I lived in FL from 1981 to 2008. The beaches are great down there, as your finds prove it. FL is driven by tourism, so the hot spots are always productive. Miami Beach / Ft.Lauderdale tend to yield some higher end jewelry... since a lot of people like to throw around there money down there to show off. But luckily for you, they seemed to throw it into the water or sand!
I was going to mention Siesta Key by Sarasota, it was already mentioned. The width of the sand is much bigger than a lot of beaches, and you can't beat that sugary white sand. Boca Grande has smaller beaches but are highly concentrated with floods of traffic since it's on an island. Lots of money out there, Burt Reynolds had one of his houses there. Maybe you can find one of his gaudy gold chains from the 80's.
I lived on the Gulf of Mexico side. The water churns more there since the gulf floor drops off sharp, so you get more abrupt choppy waves at the beaches. on the east coast, the seafloor is a gradual decline into depth, so you get long gentle rolling waves into the major beaches.
Daytona Beach, Cocoa Beach, or Panama City Beach after those crazy college folks get done with their Spring Break drunk fests. Your finds after the Spring Break rush would probably be more quantity vs. the quality of things like you show from southeast FL.