Watching footy would be the last thing on my mind in Miami but that's just me.
I love Miami get there often...easily my 3rd home behind San Francisco.
I'm assuming you'll be in the Miami/Miami Beach/South Beach area....if so Fort Lauderdale is about 45 minutes away so not ideal.
To be honest you'll have a hard time.
It's difficult enough to find a place showing the Grand Final never mind other games in FL,
they show only one game a week (typically Collingwood) and it is not live.....also not in HD.
They have an Aussie themed restaurant called Outback, maybe you can shoot them an email asking if they show games.
They have a few restaurants in the Miami area.
http://www.outback.com/
ESPN didn't renew their AFL contract this year and now the AFL will be on Fox Soccer or Fox Soccer Plus this year.
You should check their TV schedules online I suppose.
I'd also try the Australian Consulate in Miami....they will help or at least point you in the right direction.
+1-305-858-7633 (I couldn't find an email address).
Hope this helps RT.