I haven't been in the MIA
terminal for years but I can pretty much guarantee you will be taking into the sun from the terminal if you are trying to get most of the interesting traffic. If the winds are from the East, which they are 75% of the time - The European traffic land on 9 (which is south of the terminal complex) and 12 (which is west/southwest of the complex - between 1-4 pm, obviously that is looking into the sun.
Most Carribean/Central/South American stuff lands on 9 as well as the international cargo such as LAN Cargo, Centurion, Korean Cargo etc.
Looking north you have runways 8L
and 8R. Most of the aircraft that land on 8L
are American, American Eagle, Fed Ex, UPS or anything else that would use the north ramp and general aviation/biz jets.
90% of the departures however use 8R - so most of the European flights take off on 8R, but you said you were leaving around 4pm, which is before most of the European stuff starts departing. There would be a lot of other flights departing around then though. I am sure you can get a view of 8R out of the American Airlines terminal complex.