There is no public transport to the city from here. It's either taxi, shuttles or walkway across the bridge to get to the buses and metromover. Ridiculous.
When getting of the ship...Take your on luggage down to customs save yourself about 20 min...At the end of a cruise those 20 minutes will feel like a hour....
If you're taking a taxi & using a credit card to pay, ask first! It's hard to believe but Miami taxi companies DON'T take credit cards, welcome to 1970. #fail