Finding intelligent life on another planet has shifted from a long-lasting dream to an upcoming probability. The UFO sightings has become so common that it is now really ignorant to think that we are the only inhabitants of this immense universe.
If I was ever on the committee to decide who should speak for our planet, I would make sure it is a person with an open mind to accept new things in his/her life. A bigot who sticks to the values and lessons taught to him in pre-school cannot accept the fact that our lives are going to be a lot different when we give way to the aliens to enter it, and that this will definitely make some (if not all) of our previous beliefs (about the origins of the universe, etc.) sound ridiculous.
The person should give a brief but honest account of what is going on on earth. If I was to right the speech for that person, that would be something like this:
Earth used to be a beautiful magical place, but technology has pretty much ruined it. Us humans are not the only creatures on earth; there are also thousands of different kinds of animals, a number of which we kill to make food. We are so technologically advanced, but we still fight each other when we have a difference of opinion.
I think giving the aliens an honest description about how the earth is doing in 2014, can be helpful in several ways. If the aliens are willing to help us out - by prophecies or technological advantages they can offer - they must know exactly what life on earth is about. In another scenario, if they are thinking of traveling to earth and settling here, they have the right to know what an over-populated place it is, and how there is always a war breaking out somewhere.
Wickham, A. (2011). The Black Book of Modern Myths: True Stories of the Unexplained (p. 304). Century.
Gertz, E. (2014, May 7). HOW WE'LL TALK TO ALIENS. Retrieved December 28, 2014, from http://www.popsci.com/article/science/how-well-talk-aliens