As a spectator, can I bring a dog on a leash?

Yes

Yes you can...many people do.

Yes, must be leashed at all times.. But it's quite loud for dogs

Like everyone else said, yes you can, but it's a racetrack, loud and not good for sensitive dogs. If you dog doesn't get bothered by stuff like that, go for it... Great place, alot of fun.

Yes indeed.

Yes you can, but it is loud. Be careful