If a friend gets an invitation to a wedding, you can go with him/her, even if you don't receice an invitation yourself. The times of the wedding ceremony and the reception are both on the invitation. However,you ought not go to the ceremony because it is only for close family. If you really want to see it. you ought to ask first. Everyone can attend the reception afterwards. Nowadays,Indonesian women don't have to cover their heads, but they usually wear traditional clothes. There is a box at the entrance to the recetion and you ought to put money into it. But don't worry, you don't have to contribute a lot of money. And remember-at most wedding receptions you can't drink alcohol.