Been to Edinburgh as an unplanned 3 day side-trip during a 2 week visit to London, Brussels and Amsterdam:weed:. There is a a large castle overlooking the city. Like you, I went by myself. I stayed in New Town, but I had an excellent time hanging out in old town. It was during world cup. The various pubs on High street provided an excellent atmosphere to watch world cup football matches. The USA played well in that Cup, beating Mexico before being ousted by Germany.
I met some students at a pub. They brought me to a private club where I drank absynthe:00hour :00hour.
I didn't make it to Glasgow or the west coast, but have been saying since I got back that I'll return soon to visit all of Scotland and Ireland. If I dig up any potentially helpful links, I'll post 'em for you.
Have fun and more importantly avoid Haggis at all cost:SIB