Are you driving into Orlando from FLL that morning? If you are coming in via the Turnpike, you'll get off at either Osceola Pkwy or FL417. If you drive in on Osceola Pkwy you will pass directly by a Perkins at the corner of John Young Pkwy @ Osceola, and then directly past a Walmart at the corner of Osceola and Poinciana (this is the 535 location, but if you come and go directly off Poinciana you won't get tied up in traffic; that's the back entrance to the store. There is a toll basket exit @ Poinciana from Osceola; it's $.75 off and $.75 on, unmanned.)
About the tolls: from FLL, you will enter the turnpike from I595, paralleling I95 as far north as Ft. Pierce, then cutting diagonally across the state. Last I checked, that part of the Turnpike still takes cash. (The entire toll from FLL to Exit 249 Osceola parkway exit in Kissimmee will set you back less than $20. Make sure that you have at least $5 in quarters for any unmanned exits you take.) You can always buy a standard Sunpass transponder at Walgreens, CVS, or at a toll-road service plaza; they are $20+tax (not counting the tolls themselves to your credit card), and can be set up online from a cell phone. I have one to use in rental cars and my own car if I drive down, but I'm in FL at least 6X a year, so it pays for itself. There is a small discount for using Sunpass; on a trip from FLL to WDW it amounts to about $2.50. It is convenient, though, and that may be a small price to pay if that's important to you. (Note that you cannot use a Sunpass Mini sticker in a rental car, you need the standard version.)
If the drive to Orlando is the only toll-road driving you plan to do on your trip, don't buy the rental car's toll service, because they will charge the service fee for each day of your rental, even if you only drive on a toll road once.
