I recommend any place that has entertainment, a bar setting or group tables. In Epcot, Teppon Edo is a good choice because you're sitting around the chef and they put a show on while cooking the food, it's a fun, friendly atmosphere. It's also sometimes easier to get reservations there solo. The Rose and Crown can also be nice because it's a cozy atmosphere, you can get a table indoors or out, or you can sit at the bar, which makes for great people watching. The Chefs de France is also great for lunch, especially if they seat you in the glass area looking outside. There are always people and sometimes street entertainers right outside the window. In Hollywood Studios, there are a few choices, the food at Brown Derby is great and the atmosphere is upscale but comfortable, suitable for a table for one. In the Animal Kingdom there's the Rainforest Cafe right outside the entrance, which has a huge bar area with stools that look like the backsides of animals, there are TVs, tons of atmosphere and great people watching. At the Magic Kingdom nothing really stands out, they're all family oriented but totally fine for the solo traveler. Downtown Disney has tons of great options, most have bars, tons of atmosphere, great people watching, and some have live music. In particular I would recommend the bar at the T-Rex, Wolfgang Puk, or Ranglan Road, which has Irish dancers every 30 minutes or so.