How do I prevent auto-mounting of ext2 partition on OSX?
I'm no Linux buff but this Macworld article seems promising assuming you know the UUID for the volume and don't mind working from the terminal. The article wisely recommends backing up the volume before messing around too much. 

Also... Googling for Android+phone+UUID is returning links which are related to programming. Perhaps retrieving the UUID from an Android phone is a separate question for this problem.