The conversation goes like this:
Nadine: "Excuse me, do you speak English?"
Stranger: "Yes"
Nadine: "Oh good, do you know where the post office is?"
Stranger: "Yes"
(wait for answer)
Nadine: "Could you tell me where the post office is?"
Stranger: "Yes"
Nadine: "Okay, so where is it?"
Stranger: "Yes"

I have come to learn that the word "yes" has many meanings such as:
I understand
I acknowledge you are standing in front of me and moving your lips
No

Imagine how frustrating this is at work.

On the other hand, there are many ways to say "no" in Japanese, none of which include the word no. Some of these are:
I see
It is difficult
Why do you ask me that?
Perhaps you would prefer...
Yes, but...
Silence
Hesitation
Yes