re: Would they USE RADIO?
So far our galaxy has failed. Non natural radio waves have not made it to us thus far. Although we shouldn't stop trying.
Water vavour and Photosynthesis detection may be the way to go as to detecting life within our galaxy.
Here's a way out thought: I don't know what is about the Andromeda galaxy, but if there's life... transient life outside our solar system/galaxy, there's a good chance that it may be there.
