Solo and no cost limit? Yacht Club or Grand Floridian. I'd go Deluxe and with easy park access. YC is where we usually stay---my DH and I like the quiet adult feel and the walkability. By that I mean, the International Gateway entrance into World Showcase, one of my favorite places to wander, which is great alone. And the walk to MGM is nice. Also, the boats. The GF has the monorail, and I think the atmosphere there would be solo-friendly. Plus, both hotels have friendly bars/lounges and easy access to others.