English/Spanish bilingual here, I don't know how you would assess the favor you receive because no school is going to say we want you because you speak Spanish. Would it help the overrall application? Sure. But how much so, would likely be dependent on the individual application and possibly even change year to year.
I perceive my language skills as an advantage for when I am in medical school and beyond so I can help more people. For the application, it's something that's there, but no one has asked/commented/noted in any interview so it isn't overt.