According to the Developer Docs
Saving cache files
If you're using API Level 8 or greater, use getExternalCacheDir() to open a File that represents the external storage directory where you should save cache files. If the user uninstalls your application, these files will be automatically deleted. However, during the life of your application, you should manage these cache files and remove those that aren't needed in order to preserve file space.
If you're using API Level 7 or lower, use getExternalStorageDirectory() to open a File that represents the root of the external storage, then write your cache data in the following directory:
/Android/data/<package_name>/cache/
The <package_name> is your Java-style package name, such as "com.example.android.app".
More info here
http://developer.android.com/guide/topics/data/data-storage.html#filesExternal
Hope it helps