If you have one of these transponders take it with you and use in your rental car, I do this all the time. If you do not and rent from one of the majors they may have registered their cars plates with the various programs (some even put the transponders in the car). But regardless of the method they use you can then use the express tollways on either system. Yes, in FL you will come to some exits that are Sun-pass or exact change only these are usually smaller exits on not manned late at night.

I live in Pa so I have a EZ-Pass , I just took it with me on a trip to Boston. Why becasue the Rental car companies also make a profit (per day @$3) when you use their transponder. I am going to FL next month and already have my Sun-pass in briefcase for use their. And to take matters to the extreme I also have a E-470 pass for Colorado which I take on trips their.

When registering just use your normal Tag and address and then use it on any car you rent.