Today I installed Google Music app in my Samsung Gio and also activated my google account on it. Going through official way, its not possible yet since Google Music is available only in US (you'd see a sorry message if you try logging in at music.google.com). However, if anyone wants to taste Google Music in Pakistan then follow these steps:
1. Download and install Google Music's apk from web (xda forums etc.) on your android mobile.
2. Download and install Music Manager on PC.
3. Download and install TunnelBear on PC and after completing its registration, open music.google.com. Log in with your google id and pw. This time you won't see that sorry message.
4. Open Google Music on your mobile and this time it will sync it with your google account.
5. Start uploading your songs via Music Manager and fill up space for 20k songs.