When I went to my job interview, it was the first thing I told the boss and after that she was very understanding and all of the managers where I work have been extremly accepting and tolerant. Maybe this is rare, but I think if you go there with a realistic attitude and you tell it straight, it wont get in the way of their impression of you. I dont know you personally, but I find people with shortcomings such as a speech impediment are incredibly humble and just nice in general, I wish you luck and one thing that helps me cope and just comforts menin times of stress is: "this too, shall pass"