When is the right time?
My husband and I were married at a relatively young age for our social milieu and Reform Jewish/Buddhist backgrounds--we were 23 and 24. At the time, I remember thinking how very odd it was that the act of marriage was in some way, at that age, rebellious--or at least sorta fringe! I'm quite sure that a lot of people thought we were too young.
5 years later, I think we can say that our "early" marriage has worked quite well for us, including for one reason that I hadn't considered when we were planning our wedding. Namely, if you want to avoid having to get pregnant during the 35-and-up years of dwindling fertility and increasing chances of developmental problems, then getting married a little sooner makes sense. Getting married at 23 meant that we had a few years to settle into life as adults together: we both tried a career path or two, we learned to run a household, we lived abroad and traveled...and having done all that, we were still just hitting our late twenties when we felt ready to start a family.
Of course, starting a family in your mid-to-late thirties also has its advantages. You are even more settled in your career and you probably also have greater financial resources. But these days, having a baby in your mid-thirties is the more expected choice (for educated professionals, anyway), so I wanted to present the other side of the coin here.
[Postscript: Although this post is about planned pregnancy, it's important to note that about half of all pregnancies in the United States are unplanned. Education and access to affordable birth control can help women avoid becoming pregnant when they don't want to be; Planned Parenthood is an organization that provides such education and access, as well as counseling and access to abortions. Medical Students For Choice is another organization I've been involved with, which advocates for and supports reproductive health education in medical training. Please support these organizations if you have the means!]