Departing Mexico City airport to USA with permanent resident

Hello All, I always fly out of Ixtapa airport with my USA passport and Mexico Permanent Resident Card. I am required to go the immigration office at the Ixtapa airport before I board the plane and sign a ledger. So now I am departing from Mexico City airport....do I need to find the immigration office at the Mexico City airport and sign a ledger there? Thanks in advance for any info/ direction/ experience. Saludos.