Language. That's a big problem in the Miami area. Not just language spoken, but not understanding WTF you are saying or being asked. I was 5 miles south of an airport inbound to land and I heard a pilot call out "XXX traffic, cessna 152 N123AB is 5 miles
LEFT of the airport." Left of the airport?!?!? I tried a few times to figure out where he was. Asked what his compass says, what do you see in front of you, but unfortunately communication was a barrier to helping him. The pilot didn't have a clue how to navigate.
The alert areas in Miami are a disaster. There are four of them, A-291A, B, C & D. All over swamps with no real distinguishable landmarks, unless you're really a local and have the local knowledge of stuff like "Old Man Wilson's Farm", the Eastern 401 and ValuJet 592 crash sites. Broadcasting on 122.75 and making this radio call "Alert Area traffic, Cessna 152 doing stalls over the alligator." doesn't do much to the transient flyer. It leaves out which alert area you're talking about, throwing in the nearest airport would be helpful, and maneuvering altitudes.
These two found out the hard way: C152 collided with a PA30 that was on an IFR flight plan and in and out of VMC while talking to the controller at Pompano.
http://dms.ntsb.gov/aviation/AccidentReports/ywiyaz5530s2guvznzkenw451/Q03252012120000.pdf