It seems like everyone has gotten this working except me! I was able to create the symlink using your script, and I even see the cache directory on the external SD card. The odd issue is that the cache directory remains completely empty no matter how many songs I store offline. Even when I remove the symlinks, the files are not in /sdcard/Android/data/com.google.android.music. I have gone so far as to factory reset my phone twice (in two different ways) and the issue still persists. After factory resetting, my main goal was to just find where the offline files are being stored so I didn't even create symlinks.
I am using a Verizon Samsung Galaxy S3 with the stock rom.
Can anyone help me with this? Any help would be GREATLY appreciated.