Sorry I can't help you with a place on Saturdays, but you made mention of Florida and I wanted to make a comment about Florida on Saturdays. This could conceivably even impact change houses in other places.
I went to the guy I usually go to last Saturday and he wasn't there. There was another guy who I've never dealt with before in the same place, and he took me to the same little shop as usual. When I entered, they gave me a price of 5.80!!!!!!! I was shocked - I'd been going to these guys for quite some time and couldn't believe they'd give me such a low price. When I complained, the girl said it was because it was Saturday, that everyone gives low prices on Saturday because many places aren't open and all the tourists are out. I really needed to change a bit of money and argued with them about being a repeat customer that gave them lots of business and they relented, giving me 6.10 (which still wasn't quite as good as normal, but good enough).
Thinking about it, I reckon I've never changed money on a Saturday before last week.