I am a British student currently living in Kissimmee and try to avoid taxis where possible. They are expensive, much more so than at home. You didn't say how many people were travelling but if there are just a few of you, give Mears Transportation a go (
http://www.mearstransportation.com/ShuttleServ ices.htm). I paid $20 for a one-way ticket to my accommodation back in January and a return could be booked for only a few dollars more. The majority of hotels around here will offer complimentary shuttle services to the major parks. Despite what some might say, Orlando is doable without a car.