Engalana comes from the verb engalanar, which means to adorn, decorate, or grace. It's a more formal and poetic word than simply saying "decorate."
In this song, the singer uses it to express a deep desire for his beloved to "grace" his night and morning with her presence, making his existence more beautiful and joyful. It elevates the request beyond a simple invitation, suggesting a profound appreciation for her presence.
Alfredo Olivas's "Y Por Qué No" is a bold and direct serenade, where he's basically asking, "Why not?" to a secret romance. He's tired of the unspoken tension and wants to throw caution to the wind, suggesting they "quitarnos esa duda de una vez" [get rid of that doubt once and for all]. He's ready to "burlar la sociedad" [mock society] and "ir en contra de la ley" [go against the law] that keeps them apart.
Alfredo is laying it all out, proposing they give passion a chance. He's pretty blunt, asking for a date "en una cama" [in a bed] to "cerrar el trato" [close the deal] and fulfill his immense desire for her. He even playfully corrects himself, saying, "ya no soy alfredito, soy alfredo, pero solo para usted" [I'm not little Alfredo anymore, I'm Alfredo, but only for you], emphasizing his maturity and serious intentions. He's convinced she feels something too, saying, "algo se trae entre piernas" [she's got something going on between her legs], and he's ready to ignore any age differences, insisting "este niño ya no es niño" [this boy is no longer a boy]. It's a fun, confident, and very direct plea for a secret love to finally come out into the open.