I don't mind telling anyone my birthday and I turned 53 in November, too. I weigh the same as I did in HS, but a lot less than I did when I was 21. Definitely in better shape!
I ignored the AARP, too, because it's just kind of creepy to me, like some kind of monolith, that finds us as soon as we turn 50. I have read the mag. in the doctor's office and it seems OK. My husband is going to join though, because we are going to use the discounts when I stop working and I can't qualify for the NEA discounts for auto insurance and the health club.