
In the Uk there is no rule preventing the showing of an in season bitch at conformation shows, but definatel;y not allowed at Obedience (would suppose Agility and Working/ Gundog Trials also, but not sure).
It will not make you popular with the exhibitors of male dogs, but does seem to be quite common practice among some breeds where the exhibitors are quite open about their bitches condition. In other br4eeeds it would appear that a lot of bitches have jsut come in on the way to the show :D
A lot of people will just keep quiet and keep their bitch deodorised and out of the way as much as possible. Some other people will be very against, while others will loudly complain, but will still bring their own bitch out.
I would think that at any given show there are likely to be in season bitches about, if not in your own breed then in others.