rjain,
I also sent an email to the US Embassy in ND regarding the PCC but did not receive a reply from them. However, my lawyer's paralegal told me that PCC for me would be valid for one year, if i don't go back to India for a visit. The general consensus on this forum, however, seems to be 6 months. Anyways, it seems that our interviews will be some time in July, so the question on the time validity of the PCC is moot.
Coincidently, I am also trying for a late July CP interview. And the paralegal told me that postponing the interview to a date in the scheduled month is not a problem. I hope he is correct.
Keep us updated on your progress.
P_L