To me it seems unlikely that you would get a D in Spanish 2 and yet be good enough in Spanish to get a sufficiently high grade on a Spanish SAT test (or on any Spanish proficiency test). I suppose that you could take a practice test and find out. However, I suspect that you are going to have to retake the second semester of Spanish 2.
You might want to get tutoring in Spanish, or get some friends together once a week to have a “Spanish lunch” (where you attempt to talk Spanish for the entire lunch), or start watching TV shows and movies in Spanish. All of this can help quite a bit.