What would you do if I spoke German?

[Cyborg Ninja]

I was just thinking of what it would be like to have this conversation in Japan:

すいません！
え？ごめん、英語が話せません。

ドイツ語を話したら、どうしますか？

Does the above sentence make sense? I just kind of thought it up suddenly.

[blutorange]

Besser wäre die Frage, was du machst, wenn ich auf Deutsch antworte!? Egal, um zum Allgemeinverständnis beizutragen, schreibe ich wohl mal lieber auf Deutsch. Also dann auf:

ドイツ語を話したら、どうしますか？

Saying this is perfectly possible, however, I am not certain that is what you want to say. Using the above question sounds like you are genuinely interested in what the one you are addressing thinks should be done in the case of you speaking German. Do you want to say something like "And how about I speak German?"? (Btw, another example of logical quoting, see the other topic...) In that case, you would phrase it along the lines of:
じゃ(or さぁ)、ドイツ語でどう？
or more politely
では、ドイツ語ならどうですか。

[Cyborg Ninja]

Nah, I really mean it as a sort of rhetorical question. I imagine a lot of Japanese assume that all Westerners speak English, and so a situation like that can come up often. Why not assume they speak Finnish, or Dutch, or Italian instead? That was also rhetorical.