How is the port of miami parking paid for, do you pay when you park or when you leave and do you have to use cash?

A quick google search yields the ports site located here. That shows $20 per day day for cars and they accept cash/cards/or traveler's checks.

Hi James. Port of Miami was a complete cluster. A traffic nightmare. My only advice is to get there early so you can park somewhere even close to the ship your sailing on. We got there around 1:00pm and had to park well over a mile away from our ship. They had a shuttle bus, but we decided we didn't want to wait for it and walked. ugh!! U pay as you leave and they do accept credit cards.