Welcome to MobileRead...
I don't have an Android myself so I could be way off base, but if you go to Preferences -> Plugins -> Device Interface plugins -> Android driver, the dialog shows a list of directories it will send to based on which ones actually exist on your device.
Code:
eBooks/import, wordplayer/calibretransfer, Books, sdcard/ebooks
Hopefully one of those will make sense to you - that's all I can offer I'm afraid...