Most workplaces have their own vernacular and humor and it's usually a little on the raw side. The best example that you can set in the workplace is how you conduct yourselves. I would be careful not to openly judge anyone. There are probably Christians in the job that you do have without you realizing it. I believe that you feel you are in a lonely and isolated environment but that may change.
I am convinced (after more than 45 years in the workplace) that the best testimony we can give for Jesus is simply the way we act, and conduct ourselves.
People will notice.
If you verbally try to "spread the word" you will likely meet with scorn and ridicule. If you are simply a good person, who doesn't get caught up in the vulgarity of "natural men", people will notice. You don't have to berate them for it, just don't join in... laughing at jokes is ok, if they are funny... if the jokes turn vulgar, you can simply smile and continue with your work. Your lack of "joining in" will speak volumes.
Some of the best examples of workplace Christians I've ever witnessed really didn't SAY much about it at all, unless asked, and usually then only in one-on-one situations. Their "witness" was the way they went about their work, and the way they treated others. To me, THAT is being Jesus in the flesh...