Shuttle buses to Disneyworld Florida from International Drive?

I am planning a 7 day trip to Orlando during the summer with my boyfriend. Having stayed on International Drive before I loved the location and its access to the nearby theme parks, however that was about 4 years ago and at the time I had visited with my parents and had hired a car. This time it will just me and my boyfriend and we wouldn't be hiring a car, mainly because we are quite young so I'm not sure if we'd be eligable. However, my question is, does anyone have any experience with the free shuttle busses from international drive to Disneyworld? Are they reliable? Thanks for your help!