Sorry I forgot to mention, when you fill I-485 application, you have to provide the home/apt address. If that belongs to a particular SC, your case will be filed in that SC, as simple as that.
After Spe11, things have changed drastically, now the new rule/proposal about this address change.
So I would recommend, rather lying on I-485, I would file my I-485 in a SC where I belongs to rather than a SC which is processing faster.
Sorry to say my friend, some times if you do silly mistake, it will haunt for a long time. Once I read in this forum, one person just applied his I-485, just ONE day before his PD becomes current. He got EAD, AP and FP also. At the final approval, INS rejected the case without a chance of appeal. This is back in Feb 2002. So be careful and act wisely.
My $.02