The flute section of just about any high school, college, or community band in the country is a girl's club and has been for decades, but male flautists are still generally welcome (and even greatly appreciated by their female fellows). For most of the first two or three years I played in the community orchestra I've been part of for the last eight, I was the only male cellist and that was perfectly fine (right now, I'm one of two). The vast majority of brass players in the USA are male and that has, as far as I can tell, always been true; but there are still a fair number that are female and they're generally accepted.
Says me, the fact that the vast majority of computer professionals are male is only a problem to the extent that women who want to enter the field are excluded or steered elsewhere. Thus the goal is to focus on interest and talent and to make sure that a girl geek is as welcome in any IT department as a girl trumpeter or boy flautist is in a symphony orchestra; to that extent, a focus on numbers and partity is counterproductive.