Don't wait for them to stop talking. If you hang around them and wait for them to stop talking, you are going to creep them out! 3 second rule buddy, states that you will "Open" a set within 3 seconds of you seeing them. 3-2-1-Go! You interupt them because you are DHVing yourself as being more important that what they have to say. You aren't being rude just establishing yourself as an Alpha Male and Demonstrating Higher Value.
It seems rude, but if you have a good opener and something interesting to say they will listen, and respond. You can do it!
CHAT