I was "out-ed" right away. Although I have no outward symptoms, let's just say it's a small town. Everyone knew something serious was up and so when people asked me how I was, I decided to tell them. I had the feeling they all knew anyway. I'm a fairly private person, so this was quite awkward for me, but I think it would have been worse to try to keep a secret, all the time wondering who'd told whom already. So maybe I'm serving as an educational poster child about MS!
My husband had a real need to tell friends and relatives right away, so I let him. The diagnosis was hard on him, too, and he needed support.
A few months after my diagnosis, I remember wishing no one knew because I was still getting used to the idea of having MS and it was difficult to answer all those "how are you feeling" questions. I'm used to the idea now, and those questions have gotten far and few between.
It does help that I have a very supportive work environment. If I didn't, I probably wouldn't have been so open.