"I can speak fluent Spanish."

Translation: 我能说流利的西班牙语。

[natevoelker]

会 instead of 能 is better. Both should be accepted.

[KX3.]

They are both okay.

[Winston298006]

Often people say, “我会说” to mean "I can speak," i.e., "I know how to speak." “我会说流利的西班牙语。” You can also say, “我西班牙语能说得流利,” meaning "I can speak Spanish fluently."

[trycykle]

我会说流利的西班牙语 should also be accepted.

[duckmaestro]

Is this OK?
我会说西班牙语说得很流利

[ZWSilva]

This is the response I would have given

[nao657961]

This sentence refers to the degree of attainment. 能 is better.