Desvelado is an expressive word for being sleepless or sleep-deprived, usually from staying up very late. It comes from the verb velar, which means 'to keep watch' or 'to stay awake'.
In the song, the singer laments, "por tu culpa me la paso desvelado" (it's your fault I'm always sleepless). He uses this word to capture the romantic angst of losing sleep while waiting for a late-night call from someone, a very relatable and dramatic feeling.
Ever been someone's secret late-night call? In "ME JALO", Grupo Frontera and Fuerza Regida tell the story of a guy who knows he is just the side piece—and honestly, he does not care. He catches her lying when she saves his contact under a fake name on WhatsApp ("Vi que me pusiste otro nombre en el Whats" [I saw you put a different name for me on WhatsApp]) and calls him only when her main boyfriend leaves ("Que tú me llamas cuando se va ese pelado" [That you call me when that guy leaves]). Even though he is losing sleep and knows she is only using him to misbehave ("tú me usas pa' portarte mal" [you use me to misbehave]), he plays dumb and rolls with it.
The magic of the track is packed inside its heavy Mexican slang. The title phrase "me jalo" literally means "I pull myself," but colloquially it translates to "I'm down" or "count me in!" Pair that with "en corto" (right away) and "dime qué tranza" (tell me what's up), and you get the full picture of someone who drops everything the second his phone rings. As soon as she says "Vente p'acá" (Come over here), he replies "le caigo" (I'll drop by) without a second thought, trading a good night's rest for a forbidden rendezvous.