I talked to someone from México and when I was talking to him about my trip he said in reply " que suave" . I asked my mexican friends what it meant and they said it's like "cool" but they didn't know in what era it was used. Could anyone tell me?
As a Native mexican, I can tell you from my personal experience that it was more common to use that expression on the 80's/90's than it is nowadays, as it sounds kinda outdated. But it's much older than that.
For example there's the movie "Fíjate qué suave" from 1947, featuring the comedian Manolín, which used "Fíjate qué suave" as his catchphrase even before before the movie.