Many Churches are in this category.
No, only one church is in this category - the LDS church.
However they are required to post a sign on the entrance saying "No Guns". I have yet to see such a sign on a church. I wonder if they can make it stick if they don't post the signs?
No, they are not required to post signs. They only have to inform the public. This can constitute the letters they've read in congregations, posted in newspapers, etc. This ONLY applies to LDS churches (and any other church if they were to take the necessary actions, but none have).
I for one don't want to risk losing my CFP by testing this, so I don't pack in church.
Even if you were caught, it is only an infraction and you cannot lose your CFP for a single infraction.
Any way the PO is a no gun area since it is a federal building. I am sure we all know that you don't pack in a post office?
This one's a bit tricky. It actually is not clear that it is illegal. The post office policy says, "unless otherwise legal to do so" you can't carry. This is to allow LEOs to carry there. Well, if I have a permit, it is also legal for me to carry. But, this has not yet been tested in the courts, so nobody really knows if it's illegal.
But, concealed is concealed, right?
Is open carry legal when fully loaded with a CFP? Some argue it is not. The LEO who was my CFP instructor, said, "When you have a Concealed Carry Permit that means carry cancealed!" He was of the opinion it was required by law to conceal the gun.
It is perfectly legal to open carry fully loaded with a CFP. The attorney general has been asked for clarification on this matter, but in reading the law and the BCI web site, it is not illegal, thus making it perfectly legal.