Translation:I can't speak Spanish.
Duolingo gives too much credit to 会 as "future tense." Chinese is way more likely to specify a time instead of giving a tense. Or if the tense is known from context, then any time words can be omitted. If they wanted to say, "I won't speak Spanish," they probably wouldn't think putting it in a future tense, instead maybe phrasing it as "I refuse to speak Spanish," or "I (will) try not to use Spanish," or whatever, depending on the need of the context.