what do you mean by "buttons"? To me any "button" on the screen is a sprite or other game object (sprite text, for example). They always work for me. The audio commands should work.
Or are you talking about android buttons like the back button? The physical ones? If so that's good to know, but yea kinda off topic
I'm surprised though that C2 doesn't have a way (that i'm aware of) to use android buttons. There is no "android" game object to add into a game to access it.. like the one that thehen made for Windows Phone 8.0
Last statement for this off-topic button thing
Yes you can directly insert buttons (not as sprite) in C2. But this "Buttons" will not appear if you compile your project with CocoonJS. Just double-click in the white editor area and look for "buttons".