I have yet to see anyone ride bikes outside of the Resort they are staying at. Many of the roads at WDW aren't that safe to bike/walk along because of traffic. The road system consists of highways (ex. World drive), main thoroughfares (ex. Buena Vista drive) and smaller roads (ex. Community Drive). You will have to navigate all this while dealing with many buses and cars.
From the BCV you might be able to bike the path from there to MGM very easily, since that is a walking path. Also, from OKW to PI there is a walking path you could bike along. The problem is getting from BCV to OKW safely by bike.
If you are used to biking in a busy urban area you might try it. Otherwise, restrict the biking to within the Epcot Resort area only.