Presumirle comes from the verb presumir, which means 'to show off' or 'to brag'. In this song's romantic context, it's a sweet and proud declaration.
He sings, "Y presumirle a la gente que estoy enamorado" (And show off to people that I'm in love). He's not just happy to be in love; he's so proud that he wants the whole world to know, making this a unique and charming way to express affection.
Ariel Camacho does not do subtle, and in "Me Gustas Mucho", he lays all his cards on the table. The song is pure, dizzy infatuation packed into Regional Mexican acoustic guitar riffs. Right from the start, he claims he likes this girl so much he is ready to trade his own life for her: "Que soy capaz de darte mi vida / Sacrificarme por un beso tuyo" ("That I'm capable of giving you my life / Sacrificing myself for a kiss of yours"). It is a bit dramatic, sure, but who hasn't felt that rush when they are completely smitten?
What makes this track so endearing is that he just wants the whole world to know he is head over heels. He dreams about walking around arm in arm, singing "Y presumirle a la gente que estoy enamorado" ("And brag to everyone that I am in love"). In everyday Spanish, presumir means to show off or brag, so he literally wants to flaunt his happiness to total strangers. Between admiring her smile with "Eres divina / Con tu sonrisa que me fascina" ("You are divine / With your smile that fascinates me") and repeating how much he loves being by her side, the track keeps things simple, sweet, and wonderfully loud.