my polo bike is set up 35x22 single speed. I bought a smaller beater frame that I threw some various parts on.

Alot of people ride fixed, but I would say the majority ride single speed. Its all about what you are used too. You can be more maneuverable on a single speed (i.e. pedal strike)

If you are on the west coast you will probably be riding a mountain bike, if you are on the east coast, converted track or road frames.