I have anexus 7 tablet also and was having this same issue but fixed it.
First of all uninstall the game. Then download and reinstall. When you open it for the first time make sure you allow the entire content to download. Don't let the screen turn off and don't touch anywhere beyond the download dialog because then it will disappear. After it finishes exit the game. Go into your applications menu under settings and select gta. Click force stop and then clear cache. When you open the game again sound should work for everything.