There are also Specialty dog shows where you can show your dog that is spay/nuetered as well.
You would be showing in the Junior Handler ring as Lizmo pointed out as well.
Intact bitches can be a lot of work. You have to make sure - while in heat you keep a consistant eye on them. They have a higher chance of getting Pyometra as well - which can be deadly. We have seen three cases come into work already and two have been fatalities.
An intact male is also lots of work - you have to ensure they have good behaviour around intact females.
Having a fixed dog is SOO much easier! haha
I have in intact Belgian Tervuren male that I show.
Another thing about bitches that come into heat - you really shouldn't show them when they are in heat. Its legally allowed through the CKC in conformation shows but you are NOT allowed to show an intact bitch in any obedience competitions.
So that sort of puts you back a bit as well.
Its a big decision