As a Republican (that is, an Australian who wishes to have an Australian head of state instead of the Queen... as opposed to being a member of the American Republican Party) it may seem strange but I actually think that singing God Save The Queen during the opening of the Commonwealth Games is enitrely appropriate. Advance Australia Fair may be our national anthem, but the games will be opened by the Queen, our head of state.
After all, when we had that referendum back in 2000, the majority of Australians voted for the Queen. In their wisdom, the Australian people felt that having the Queen as our head of state was far more preferable to having a Republic - even the proposed one that was imperfect and could have been changed at a later date with another referendum.
No, the majority of Australians voted for the Queen of England to be our Queen and head of state. As someone who voted for a Republic, I must nevertheless acquiese to the rest of the country's wishes and therefore state that God Save The Queen must be sung at the Commonwealth Games.