I agree with, and am following the same path as Joanna. I have told my wife, son, daughter and about another 15-20 folks or so. I retired from teaching a few months ago (simply hated being subordinate to my vindictive Vogon inline manager) but when I was still working I told the Headteacher and two of her deputies. That seemed the right thing to do as day by day I was increasingly presenting as female: hair make-up, jewellery, woman's shirt trousers shoes. I don't hide from the neighbours when I am out and about and just talk to them as I normally would. I actually said to the gender psychiatrist that I had no intention of making some bold coming out statement to the world because I thought that would be rather unnatural and melodramatic and he saw where I was coming from. Soon (if the postman hasn't been kidnapped!) I will be starting oestrogen which will bring about further change. Should anyone ask? I'll just play that by ear and to be honest it is not something to which I give a great deal of thought.
Ask yourself this. If one of your male friends started to dress like a woman and wear make up jewellery, breasts started to grow, face changed.............would you feel you had to ask? Unless they were hallowe'en devotees it would be kind of obvious. You'll be fine