Por los suelos literally translates to "on the floor" or "along the ground". It's a highly expressive idiom that captures a feeling of being completely overwhelmed by emotion.
In the song, Xavi sings, "...por los suelos me traes" which means "...you have me head over heels." He uses this dramatic phrase to convey that he's so infatuated, he's metaphorically weak at the knees and completely floored by his love for this person.
This song is a super sweet and direct declaration of love. Xavi is completely smitten with a girl, especially her "ojitos de color de miel" [little honey-colored eyes]. He lays it all out, saying he's dying for a kiss and wants to be the person she sees every morning when she wakes up. He's so into her that he claims he'd give up everything for her, even smoking... before immediately taking it back with a funny line: "Obvio eso fue mentira, poquito nomás" [Obviously that was a lie, just a little bit].
He imagines a perfect, chill life with her. They'd watch the sunrise together and get lost in space, smoking next to the stars. It's a simple, romantic fantasy. But even with all the beautiful things in the universe, he says nothing is "Más hermoso que tu cara y el café" [More beautiful than your face and coffee]. When he's with her, time slows down and his problems just disappear. It’s a straightforward love song about being so crazy about someone that they become the center of your world.