Heading east on Florida's Turnpike to Disney, say, from I-75, you get off at Toll 529 (Western Beltway) heading south towards Tampa. This is before you reach I-4. About 12 miles and one toll plaza (use the "exit ramp" for cash tolls) later you get off at Hartzog Road and head east (becomes Western Way). You will end up on Buena Vista Drive near Coronado Springs and Blizzard Beach.
There is no real shortcut to downtown Kissimmee this way; if you skipped Harzog Road then the next major interchange (after another toll) is Rte 192 (Irlo Bronson) (you're in west Kissimmee) and after that is I-4.
