In 1977 the two Voyagers spacecrafts, were launched including in each one, a gold disk with the sounds and images of Earth. Possibly, the better idea would be no send any message with information from us. Anyway, from the invention of radio and TV, we are sending signals to space day to day. So, is too late.
My message could be "Aliens, don't come to our home, 'The Earth'. This humanity is very crazy and they are very dangerous."