I live in Wichita and I don't know any other atheist personally here. This really sucks. I am in a crochet class at the local extention service and all of the ladies in my group are christan or catholic reppublicans. They have made all of these points very clear. They don't know about me being an atheist, I know I would be asked to leave and not come back. So I just avoid certain subjects and don't talk when there talkin about religon or politics.
Basically, you're moving to an okay area of Kansas to be if you're an atheist. Lawrence would probably be ideal as it's a college town and more "progressive". You'll have a MUCH easier time there in Overland Park than you would in some of the smaller towns out West and South of there. I grew up in Olathe, which is just next door to where you'll be (I'm in Lawrence area now). I went to gradeschool with ONE openly atheist kid and he never suffered for it, so I doubt you'll run into any immediate conflicts. At worst you'll have to put up with hearing about a lot of pro-lifers and anti-homosexual types in the news/politics. You'll be fine, Overland Park is part of a pretty large metro area. Also, I'm 99% sure there are a few atheist/freethinking groups in the KC area. Good luck and welcome to Kansas: As bigoted as you think! (play on the official state motto "as big as you think")