If you intend to wear the kilt later on when you are working with these people it is probably best to let them see you in the kilt from the first time you meet. That way it won't give you a problem later when you want to "come out" as a kilt wearer. I can think of many people who have only ever seen me in kilts and now expect me to be kilted. If you have worn your kilt out and about with your girlfriend you should not have a problem wearing it in front of co-workers or new colleagues, you'd be surprised how many strangers might recognise you as the guy in the kilt whom they have seen on the street and they might be more surprised themselves if you now turned up unkilted.