First of all, schools do not take into account AP scores generally when admitting students. So, if you do poorly, it does not affect your chances. Since you'd be taking it senior year, it wouldn't matter anyway. If you say you're taking a difficult class at the start of senior year, like an AP, colleges will know if you drop it and they will also see your grade when your midyear reports are due in February. That's after ED, but if you're deferred or something, they would know.
Regardless of the fact that AP scores generally have no affect on admissions, yes, do it. If you want to impress them with your skills in Spanish for admissions, they'd rather see a Spanish SAT subject score.