In my experience, Gorgonzola (& other blues) will develop a definite ammonia smell, as well as a sharp, sometimes bitter, unpleasant flavor when they're way past their prime. There's no mistaking either one.
I have found that the nose beats the eye in the case of spoiled blue cheese. One whiff is all it takes (and you will never forget it...). Personally, I have never had blue cheese be bad and smell a;right, but maybe others have had different experiences.