Possible Clues:

• “I met her in ____, in old Mexico” (Frank Sinatra, on his Songs for Swingin’ Lovers album)
• Northern Mexico metropolis
• City of Mexico
• Capital of Nuevo Leon state in Mexico
• Fear gold's not included among assets in one part of Mexico
• Mexican city making tin, not half horrible to enter
• Mexican city
• City's awful, half buried in cash