I'm planning on going to London after the empeg meet (Sep 18 - Sep 22) and I was thinking of staying at London Marriot Hotel County Hall. Whould this be a good location if not planning on renting a car? If not what whould be a good Marriott Hotel to say at?

Also any recommendations on other things to do, this is my first time out of the US.

Yup. Very handy for tube and train so you won't have any problems getting around.

Here's my recommendation for nice, but cheap(!), accomodation in the heart of London: Citadines Trafalgar Square.

I've stayed there for multiple nights on two occasions now, and the location is hard to beat. It's right beside the Charing Cross and Embankment tube/train stations, less than a minute's walk from Trafalgar Square, very close to Leicester Square and the theatres of London's West End, 5-10 minute walk for Soho night life, etc..

And a reasonably "safe" location, being right beside Whitehall, and a molotov's throw from Tony Blair's house -- lots of coppers around to keep the world tidy.

Cheers