I have always been told that the second I go off birth control I better be ready to get pregnant. I think it is more convenient for the doctor to have you wait in order to calculate due date, but that's it. I did conceive the first cycle after bc, but it was a chemical. Also, your cycles could snap back to normal right away, but I've had several friends have totally out of whack cycles for several months (most get an initial cycle and then nothing for months). I had 90-100 day cycles before going on the pill and resumed a 50-60 day cycle after going off. But that's me. Just like everyone responds to the pill differently, everyone also responds to going off the pill differently. I don't think there's a medical reason to wait though. I'm actually a baby that was conceived the first cycle after my mom quit the pill when her doctor told her it would be a year (that was 1982, though). I know lots of babies that are right-after-the-pill babies. The rule of thumb (and not very helpful I might add) is that while it could take up to a year for your cycles to resume to normal, you could get pregnant immediately.
As far as the pre-con appt, I don't think it's necessary unless you have issues that you need to address with the doctor. I personally needed to do it because I have PCOS and a family history of endometriosis. I expected to face infertility and wanted a documented "start date". Otherwise, I think a prenatal and folic acid is a fine way to go.
I also again want to suggest "Taking Charge of Your Fertility" by Toni Weschler. I don't have a lot of women in my life to discuss this stuff with and the book is so informative!! I became so in tune to my body after reading it. You don't have to chart or temp, but it helps you understand your cycles and possible ovulation signs much better. With PCOS, my doctors just assume I don't ovulate naturally, but I do. I wouldn't believe it unless I had read the book and charted, though. I was totally clueless before reading it and it was like a lightbub went off.
But really, going off the pill is just a big game of "wait and see". Be patient, relax, be knowledgeable and baby dance a lot