Car rentals tend to come with an E-Pass/SunPass system that for $2.50/day of going on any tolls, plus the actual toll costs saves you from having to manually pay the toll (as of June 2011 and based on my understanding).
You can make it around Orlando/Kissimmee fine without using the toll highway system. If you come to the townhouse without using tolls you are looking at about an hour drive, using tolls, it will cost ($3.50 if you manually pay the tolls, $6.00 if you use the car rental autopay system – June 2011 pricing, prices will change). It takes about 40 minutes to get to the townhouse using toll roads and roughly an hour if you don’t take any toll roads. Note that the main road out of the Orlando International Airport is a toll road and you pretty much have to try not to get on that toll road.
If you don’t take the toll road to the town house, and are new to the area, I suggest taking International Drive for part of the route. Not to save time as the route is full of traffic lights and traffic. However, International Drive is a great street with lots of stuff ‘going on’ if you want to do a bit of sight seeing on the way to the vacation rental. West Irlo Bronson Memorial Highway (Hwy 192) is another street with lots of touristy stores (some a bit seedy but overall harmless from what we’ve experienced).
Other than the drive from the airport to the townhouse you likely won’t experience toll roads while driving around the Orlando/Kissimmee area doing touristy things. Although, we have used toll roads to save a lot of time heading up to swim with the manatees in Crystal River. You can easily make it to a number of the Atlantic or Gulf Coast Beaches without needing to use toll highways.