I have just learned that the taxis have a set price from "Miami Airport to Port" for $24.00 - I have been paying my T/A more then this to take the bus. When taking the bus we wait until the bus is full before leaving then waiting to get off at port. To me taking a taxis seems the better we to go.

Sure are the way to go. We have said this before in this forum. The "set price" is not exactly that. There is a port entrance fee the taxis/limos get charged and their could be a long wait in line to drop off which the taxi will charge you for. BUT, if you have more than 1 person in your party, the taxi is cheaper AND you don't have to wait on the bus.
You can get the airport taxi attendent to get you a large taxi (van or suburban) if you have a lot of people/luggage. We fit five (3 adults 2 kiddos) in a Suburban taxi without too much trouble.

this may help
http://www.miamiairport411.com/transportation.htm

When going straight from the Miami airport to the pier or pier to the airport, it is a flat fee of $24 period. The only additional is whatever you want to give for a tip. You are not responsible for any tolls, or waiting time. If a taxi driver tries to charge you for anything extra I would get his driver number, taxi number, and report him. It is clearly printed on the sign posted on the window in the rear passengers seat, that the cost is a flat fee and includes all tolls. The driver's number and taxi numbers are usually posted on the dashboard, or sometimes on the glass divider in the taxi if it has a divider. I write down these numbers whenever I get in the taxi because I have had to report a driver.