Balanço literally means "swing" or "balance." It's an interesting word because it evokes a sense of movement and rhythm, which is central to the song's theme of love.
In the context of "Num balanço de amor" (In a swing of love), it beautifully captures the back-and-forth, the ups and downs, and the delicate equilibrium of a romantic relationship. It's a poetic way to describe the dynamic nature of love.
Leo Middea spends the first half of this song listening. He looks at someone and decides their eyes are the reason to believe in the future, then stops talking about it: "Me calo" (I keep quiet), because sometimes the sound of words needs the silence around them first. It is an odd thing for a songwriter to admit, and he admits it twice. "Mas eu gosto do som das palavras" (But I like the sound of words) is the closest he comes to defending himself, and even that is about the sound rather than what the words mean. The chorus is an invitation repeated until it sticks: "Vem cá dizer" (Come here and say it), "Num balanço de amor" (In a swing of love).
Then Curandeira answers in Spanish, and the song stops being one person's thought. She takes the same opening image and turns it inward: "El eco de tus sentimientos" (The echo of your feelings) is something you hear from inside rather than out loud, which is the reply the Portuguese half had been waiting for. Her closing lines are the least shy thing here. "Me levanto con fuerza y sin miedo" (I rise up strong and unafraid) arrives right after she admits she likes falling into his arms, and neither idea gets walked back.