Mexico City has been my favorite place in the world for many years. I briefly tried to live to the North of MC, in San MIguel d'Allende, and found it to be quite pleasant for foreigners except for high prices and the dry dusty climate. I have travelled to Mexico several times a year for decades but no longer due to the spreading violence. Mexico City and Yucatan were safe until recently but are now infected with violence. This is causing an outflow of expats.The two major retirement communities in Mexico are Ajijic near Guadalajara and San Miguel d'Allende. I think these are much nicer than the capital of Mexico. San Miguel is lovely with a very supportive and large expat community. There isn't that sort of tight knit group in Buenos Aires. Few foreigners without family connections here choose to retire in Argentina. It's unstable and unpredictable. There is a lot on this website about renting flats (prices will be in dollars for non-locals who cannot provide a guarantor) and medical insurance. Given the current crisis, your father can expect a great deal of economic volatility, constantly changing prices, constant demonstrations, protests and strikes and an increase in crime. It was very unpleasant during the 2001 economic crisis and default. He can come down and rent for awhile and see for himself. Argentina produces most of its own food. I expect vegetables to be available at all times.