I have idiopathic membranous glomerulonephritis, diagnosed in 1997. I was extraordinarily lucky in my first pregnancy, and am told the outcome will most likely be very similar with my current pregnancy.
I was on therapeutic medications for a decade before I got pregnant. I've been off of them since July 2008 when I got pregnant with my son, though there was some discussion of putting me back on them until I became pregnant with this baby. Some would probably tell you to try a course of immunosuppressives to see if you could be put into remission before pregnancy. (Something I was actually about to start when I found out I was pregnant with my son!) The main factors in recommending for/against pregnancy for my nephrologist and all the other specialists I talked to on the MFM/OB side were that my blood pressure was well-controlled and my labs (kidney function and proteinuria) were stable in the time leading up to pregnancy.
Also, I at one point had a nephrologist who was sort of alarmist. He told me he would not treat me if I became pregnant. He was very comfortable treating elderly patients, but a woman of childbearing age was really scary for him. So your nephrologist will definitely matter - mine has been wonderful working with my OB both pregnancies and laying out pros and cons of medications (though the two doctors disagree about what I should be on).
I have lived in Cleveland, so I know a wonderful nephrologist there (though I saw him in college, so I can't be sure how he is in helping manage a pregnancy - I assume as awesome as he is otherwise!), but I do not know any MFMs. I could get some referrals, though, if you'd like - a friend of mine is in residency at Rainbow Babies, and I'm sure she knows MFMs.
I hope that your kidney biopsy is uneventful. I assume they're doing it with you under conscious sedation, which is quite a trip! Feel free to PM me - I'll give you any perspective and referrals that I can!