Ay, güey is one of the most common expressions in Mexican Spanish, and it's the perfect phrase to learn to sound like a native. It's a versatile exclamation of surprise, excitement, or frustration, similar to saying "Whoa!", "Oh, man!", or "Jeez!" in English.
Breaking it down, güey (sometimes spelled wey) is ubiquitous slang for "dude". While it can sometimes be used as a light insult, among friends it's a common term of endearment. In this song, the title phrase Ay, güey is used to express surprise and sets a very informal, street-smart tone for the track.
Fuerza Regida gives us a look into a wild lifestyle in "Ayy Weyy." The singer describes himself as someone who's been sharp since he was a kid, saying, "Consiguiendo feria, me gusta vivir de malandro" (Getting money, I like to live like a gangster). The song is full of boasts about partying, women, and run-ins with the police in an American neighborhood, or "vecindario gabacho." One of the best lines is when the cops raid his house looking for drugs but find something else entirely: "Pero puro disco Diamante, Platino, encontraron" (But they only found pure Diamond and Platinum records).
But it's not all just partying. There's a hint of sadness underneath the bravado. The singer admits he's drinking whiskey because his heart hurts over a woman: "Por eso es que me duele el cora'" (That's why my heart hurts). He says he chose to be single and deals with the pain by being with other women, but the feeling is still there. The song jumps between this heartbreak and celebrating the next beautiful woman he sees, which is a whole mood.