"I can't speak Spanish."
... despite there used to being two downvotes on this comment, Shawn has a point.
我不能说西班牙语, is incorrect considering 能is about having the ability to do so, 会is about knowing how to do sth, and 可 about having the permission to do sth.
The answer should be 会 。 能 is only for PHYSICAL ability, 会 is for ability related to MENTAL ability.
I was explicitly taught that 说 is redundant here and would sound stilted. Duolingo may be refreshing my vocabulary, but at this rate it will make my grammar worse!!
I was taught to say 说. Without it the sentence is just, I can't Spanish lol.
我说不了西班牙语 ought to be accepted; '我说不了’ is a valid translation of 'I can't speak..', right?