Why not? Most people don’t, but I have not heard this as specifically being “not recommended.” I think it’s awesome you want to take more than one foreign language and, if it fits in your schedule, then great.
Don’t go into it with that attitude. If you do not feel prepared for Calc BC then don’t take it. Wait until you are ready. If that’s junior year, great; if that’s senior year, also great. But you don’t want to fail and have to retake it.