At my job, the issue is not one of people openly mocking Christ or Christianity. In fact, I pretty much never hear anybody say a word about such things except for maybe one or two people.
In my current situation, I am dealing with a lot of just outright nasty people, and they normally operate in cliques or groups. What I have been trying to do, and I have had a certain level of success, is to try to isolate people from their groups and befriend them, usually through a common interest, so I might gain some sort of inroad into their lives.
For example, there is one guy who, for no reason whatsoever, was the most obnoxious jerk imaginable to me for several months. I mean, it got so bad that I literally caught myself daydreaming about getting into a fistfight with him on several different occasions, and, of course, that is never the route to go. I had overheard him talking about his favorite NFL team several times, so I got him a lanyard (one of those things that you wear around your neck that you can put your keys or ID on) of his favorite team, and I gave it to him. When I did, you should have seen the look on his face. He was totally dumbfounded, and I was actually left wondering if he thought I was gay or something. Anyhow, that simple gesture really broke down a massive wall between us. Now, he says "Good morning" to me every day, and he regularly initiates conversations with me on different topics. We have not spoken about the Lord yet, but at least we are talking.
The same thing with another guy at work. He absolutely detested me for some unknown reason. In his case, I actually asked a woman in his department who I am friendly with to sort of go "undercover" to see why he hated me so much. She did ask him about it, and he told her that he could not stand me, but he admitted to her that he did not even know why. Anyhow, I knew that he was a Yankees fan (I could not care less about sports), so I engaged him in a brief conversation about the Yankees. Fast forward to now. He goes out of his way, every day, to initiate conversations with me on different topics. I am not sure exactly what the common denominator is with these types of people, but maybe it would help if you just took some sort of initiative to find some sort of commonality between you and your co-workers, and start from there.
Of course, the goal is to share Christ, but we do not necessarily have to lead the conversation with that.
I am thinking of a woman I work with as I type this. She absolutely detests Christianity, from what another worker told me, and when she found out that I was a Christian, I could immediately sense disdain for me in her. Well, I have been very kind to her, day after day, for months, and she is definitely warming up to me, and some walls are seemingly coming down.
Sometimes we just need some kindness mixed with a little patience. It has been said that we are the only Bible which some people will ever read, so let us concentrate on being living epistles of Christ or preaching through our lives. Believe me, I am not writing these things as someone who has always done things the right way, but I am learning.