Also worth noting that at MIA, Fox is off-airport meaning that you need to take the train to the MIA rental center and then wait for a shuttle bus to take you to their location. The MIA rental center is not especially convenient to start with, and having to wait for a second shuttle just to get to a line where you wait for your car can be a PITA. Same bus-to-train fire drill on the return as well. It may be worth a few dollars more to book one of the majors located in the airport car rental center.
From Fox:
Upon arrival at the Miami International Airport, please follow the signs for Rental Cars. These signs will guide you to the MIA Mover Train which delivers all car rental customers from the airport to the Rental Car Facility.
1 - Once off the train you will enter the Rental Car Center, please walk to the left and look for the sign that reads OFF AIRPORT RENTAL CAR SHUTTLES.
2 - Proceed past that sign to the next sign that also indicates OFF AIRPORT RENTAL CAR SHUTTLES.
3 - Walk outside to the left where you will board the Fox Rent A Car Shuttle in shuttle spaces 1 or 2 for a short ride to our Miami location .
The Fox Rent A Car shuttles operate during regular business hours.
Please note: Shuttle wait times may vary. During periods of high demand like Summer and Holidays wait times will be longer.