I told my family and close friends right away but waited over a month to tell my in-laws. It was really hard because there was no way of explaining to my MIL what a PhD means -- all she gleaned from the conversation was that I was dragging her son across the country for more school. She tries really hard to be supportive but she has no idea what I do for a living. After trying to explain countless times what I meant when I talked about defending my MA thesis, I gave up and talked about buying a new outfit for the defense instead
After we told the in-laws, I made a FB status announcing that I'd accepted a place in X University's English PhD program. Since then, I've had a lot of people making snarky remarks about how I'll be going another 4-5 years without an income. I secretly love it, because then I get to tell them about my 6-figure funding package and bask in the awkward silence.