SMARTY PANTS!!!
Why do I say this?
Because people who talk fast are SMART.
I have the same problem. My mind runs so fast that my talking tries to keep up with it.
Like everyone else said, just slow down. Although, I have learned that sometimes that does not help!
Or another you say is "I know I talk fast sometimes, I just have a lot of energy. Can you tell?!" That can break the ice a little. Or "I only had half a pot of coffee today! Really, I did." Those things work for me. Acknowledging it and having fun with it will make you and them feel comfortable. But, don't dwell on it too much. They are just as nervous and excited as you are!
Hope this helps!