Pisteando is a colloquial and very common term in Mexico and other Latin American countries for "partying" or, more specifically, "drinking alcohol."
In the song, the singer uses it to reassure his partner, saying, "No te mortifiques porque ando pisteando" (Don't worry because I'm out drinking). It's an interesting word because it's informal and gives a glimpse into everyday Spanish slang, making the lyrics feel more authentic and relatable.
Get ready for a fun and flirty declaration of love with Julión Álvarez Y Su Norteño Banda's "Atento Aviso"! Our singer is sending out a "formal notice" that he's about to have a good time, maybe even change his name because he's going to get really drunk. He warns us, "Este muñeco con poquito tiene pa' ponerse necio" [This doll doesn't need much to get stubborn], especially when he's "aferrado y enamorado" [stubborn and in love].
He wants his love interest to know that he's hers, he adores her, and he transforms into a crazy person for her. He even gives a heads-up: if he calls, don't reject it, because it's just to tell her he loves her. If she hangs up, he's coming to find her and wake her up with a serenade! He knows she likes him when he's had a few drinks because he gets "en modo cariñoso" [in affectionate mode] and starts kissing her. And honestly, he thinks about her most when he's drunk. It's a playful, passionate, and very direct confession of love, all fueled by a little too much to drink!