Is there a map of the vendors? Are they generally separated by what they're selling? Or is it a free for all?

Free for all

No map. Separated by what they sell.

Many vendors have a semipermanent location where they are set up, but so many vendors vary, or spring up as one-offs that to have a map would never be the same twice. A good guideline is that new merchandise is closer to the parking lot, and used items are closer to the road. (Nearer to the stadium)