My parents stayed in Mexico after their Medicare and SS kicked in.

Once you've been down there for 5-10 years, why would you come back? There are huge communities of retired expats in Mexico. We're talking 5-10k expats all visiting the same grocery stores, churches, etc.

My parent's best friends down there grew up in the same era they did, often in the same regions of the US. I don't know what my parents would come back to the US for?