I'm an Agnostic Atheist and I'm open about it. As long as you're not the militant type and respectful of people beliefs, you have no need to be scared of coming out, most people will not shun you. Of course, there are few that will pick a fight with you, see you as the embodiment of evil and think of you as just plain retard(Ignore this type). But that shouldn't make you put on a mask and pretend to follow something you don't believe in.