They're stored at the following path:
/data/data/com.your.package.name/shared_prefs/packagename_preferences.xml
If you move them from this directory, AHPreferenceActivity will recreate the default options at this directory. Without modifying AHPreferenceActivity itself, there is no way to change this path.
Note that the only way the user can actually even view this path is via root access. If a user is not rooted, they will not be able to tamper with the app, but if they are rooted, there is nothing you can do to stop them from finding the private directory. The default should be fine for most needs. If it isn't secure enough, you could perhaps try encryption.