Well, depends where you live. If you live in a small town, then the less than 5% rule applies; if you live in a big city, then throw the low number out, and it would likely be 10-15% in some places (NY, Chi, SF, Hou, Mia).
And in any event, if 5% of the popoulation is gay, you only need 20 friends to be likely to have a gay friend...