The title says it all: "Hoy me porto mal" [today I'm going to behave badly]. Portarse mal is what you'd say to a naughty kid, and Sofía Reyes turns it into a flirty, very grown-up promise. The whole song runs on one food joke. "Voy a comerte como animal" [I'm going to eat you up like an animal], "Tu boca me sabe a sal" [your mouth tastes of salt to me], and "Esto se hace sin ropa, con cuchara y tenedor" [this is done without clothes, with a spoon and fork]. It is not subtle, and that is the fun of it.
She even brings table manners into it: "Dejar la comida es de mala educación" [leaving food on the plate is bad manners], so she is going to finish every last crumb, "Chupo ca' migaja con la lengua" [I lick up every crumb with my tongue]. Here ca' is a clipped cada [each], the way people actually talk. The twist is the line "Me porto bien mañana pero..." [I'll behave tomorrow, but...]: tomorrow she's good, tonight she's not. Learner tip: cerquita is a cute diminutive of cerca, so "cerquita de la muerte" is "right on the edge of death", a dramatic way of saying this feels too good.