As a Christian, should I associate with those who shun the Lord?

I have neighbors who are somewhat friends, they are by no means religious. They're nice guys and like to have fun, but they are very anti-religious. They even have an upside down cross in their basement (which I was offended by) Should I not associate with people like this? I thought that maybe in time I could preach the Gospel to them, however I doubt they would ever listen.. they are unrighteous.