It is not advisable, nor permissible, to walk between most parks and resorts. The roadways at WDW are very busy and there aren't typically any sidewalks. This is with a few exceptions, however. You can walk between MGM and Epcot, and between either park and the Epcot area resorts (Boardwalk, Beach Club, Yacht Club, their associated Villas and the Swan & Dolphin). There is also a walking path between Old Key West and Downtown Disney and another walking path between Saratoga Springs and Downtown Disney. You can also walk between the MK and Contemporary and the Polynesian and TTC. Aside from those listed, you can not walk to or between parks and resorts on property. It's not really close enough to do so anyway, and with free transporatation, why bother?