"Atheism Week" isn't about being "anti-religion" or converting believers to non-believers; it's about demonstrating just how prevalent atheists are in society. You almost certainly know an atheist or two, but they may not consider it necessary—or wise—to share their lack of faith as readily as believers broadcast their opinions via their jewelry or T-shirt slogans or bumper stickers. As Dr. Dawkins wrote in his introduction to the Out Campaign, "...a major part of our consciousness-raising effort should be aimed, not at converting the religious but at encouraging the non-religious to admit it — to themselves, to their families, and to the world."
It's not my place to "out" anyone or to recommend actions that would place anyone in peril. If being open about your atheism could cause you to be an unemployed or homeless atheist, openness should probably wait. On the other hand, if the greatest danger of openness is that you might annoy someone, consider the possibility that outing yourself to those who know you best is a great way to demonstrate that normal, kind, loving people can indeed be "Good Without God."
† Christianity has the cross, Judaism has the Star of David, and Islam has the crescent moon, but atheism—which lacks official leaders or central beliefs other than an absence of belief in gods—has no one universally agreed-upon symbol. A red letter "A", as suggested by Richard Dawkins' Out Campaign, seems to be catching on, though.