Me and my partner have a day long stopover in Miami in October, so we're hoping to visit the city for the day instead of staying in the airport. What's immigration like there, do you know?
If you intend to spend the day at the beach you won't go wrong heading to south beach and the taxi ride is a direct shot (~$20). Don't rely on public transport for anything. October is still hot and humid (hurricane season is still winding down) and the buses are only 10 minutes late if you are lucky.