There is a lot of great Mexico information on Billy and Akaisha Kaderli's web site:
Retire Early Lifestyle
They sell a web book about living in the Lake Chapala area, which is probably the most popular retirement area in Mexico for North American retirees. I can definitely recommend it. It is worth reading now, during your knowledge acquisition process and can help you plan a trip.
Both how well you speak Spanish and how well you plan to speak Spanish within a period of 1 year after moving will help determine your range of suitable locations. Also, whether you are getting some kind of pension that would qualify for a visa. Thanks to cheaper air tickets, Mexico is not even necessarily the "closest" Latin American location to Philadelphia, considering costs and travel time.
I am writing this from Medellin, Colombia which I think should be on the map for many retirees. Perhaps ironically, I would consider it safer than many retirement locations in Mexico and Latin America. But I can't get a visa to stay more than 180 days per year since I don't have a pension, wife, business, or $200K+ property.