
The Greyhound breeders I have met have been lovely, it's a numerically small breed in the show world so most people know each other well.
This does sometimes mean when your new you feel like your butting into a tight circle, but most should be eager to welcome a keen newcomer, especially if they are the right (lower) side of 50, as without such people breeds can't flourish and continue.
Try to be brave and introduce yourself to your neighbours at Crufts and they will hopefully introduce you to the rest :)