I think that is the presumption. When we first started SETI type programs, we were looking for certain signals that matched our own. TV, radio, mathematical probability and repetition, etc. We assumed that other civilizations would be sending out signals that we could pick up, after we realized that all our own radio and TV transmissions could be intercepted by any other civilization at or above our own capabilities. Ironically, the first radio broadcasts that might be picked up by ET's were Adolf Hitler's speeches on German radio. Great introduction to the human race! Of course, if they don't speak German, it would come across as maniacal outbursts and soft afterthoughts, on an emotional level.
Were they to analyze our TV program broadcasts, they'd see racial examples of Amos and Andy, and then I Love Lucy, and then Lost in Space. Surely, they would be quite confused and concerned as to what this planet was really like! Then when they saw Star Trek, they'd be scanning their exosphere for starship orbits and landing parties.
Should anyone ever pick up the Pioneer spacecraft, launched in the mid-70's, they would be treated to a CD (the first one IIRC) of earthly sounds and images of Earth's life forms. Also mathematical calculations, great writings of literature, and Einstein's theory of relativity (E=MC2).
Yeah, the aliens will basically think we are irrational nuts. If they saw the YouTube videos of Area 51, they'd be shaking in their boots!