Hi ,
Normally the info record rules will be like if you checl the info update indicator it will update the info record if alreday exists or cretes if or exists at Plant level .
Though info record conditions comes into a PO when create the PO for that material which have info record , system will always allow to chenge the conditions /price in the PO .
If you do not want this is to happen you can always create the PO with reference to a contract or you can maintain the pricing condition record at MEK1 to get defaulted in the PO.
Regards,