I think in FLL there's a UA club which is what you'd use. At MIA though the only * lounges are for J/F on LH/LX if I'm not mistaken.
I think there used to be a contract lounge with TAM but then TAM left the alliance and I think that changed things.
I hope this changes, there's enough UA/CM/AV/AC traffic in MIA to have something, but I'm not there often so I guess it doesn't really matter that much to me in the grand scheme of things.