I haven't been to Miami In 5 years, so I don't exactly remeber that specific area. But there are several around WDW that don't have a person to pay. You either need exact change or a Sunpass. Your friend might be talking about the express lanes where there are no booths and you just drive and there are sensors above. If you don't have a Sunpass you have to go off to the right and pay the toll to a person. There are a few of these on 528 around the airport in Orlando.
We bought a Sunpass bc both of our parents live 45 mins north of Orlando and we visit often with rental cars. It came to the point where we had to travel with a bag of change to pay the tolls so we bought the Sunpass. This was back in 2006 or 2007, and at the time we had to pay $25 for the Sunpass device. Not sure if its the same 5+ years later, but they do sell them on the turnpikpublicans and a few other places.
I believe if you use a rental car, you can ask for the unpass to be activated for your rental period. You are only charged for each toll, not a daily fee. We just had to be careful bc our Sunpass was charged and then we were charged again by the rental company for the tolls!!