Pop Century has WDW bus service to all the parks. There is a bus stop outside the main building where the food court/gift shop is. Normally, buses run every 20 minutes or so (a little longer during the mid-day). They will bring you to the bus depots just outside the turnstiles at each park.
All Disney buses are crowded first thing in the morning and at park closing, but they shouldn't be too bad the rest of the time, especially that time in August.
Have a great trip!