There are currently two carts that may operate at the same time... or not.
One is in Frontierland, near the Mark Twain, in front of the Golden Horseshoe -- they have turkey legs and chimichangas (fried burrito).
One is in Tomorrowland, between the Matterhorn & submarines.
I keep meaning to get one, but sometimes I get a corndog, and those are sooo filling!