Yes, it is. “您” is a very safe word. But be careful, some girls look older than their age, some of them would be feel terrible when you greet them by "您好". It's no standard answer. If you really meet the person who is angry at you (you greeted him or her by "您好"), you can say "对不起。. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.