Getting started

At 73, I want to leave the US and keep considering Mexico. I have been researching cities to visit that might be suitable for me (climate, safety, etc.) and if Mexico would be for me. I’d prefer not to be in a large ex-pat community but experience Mexico. I lived in Spain long long ago, and was fluent in “Castilian” Spanish. Questions: Suggested “walkable” cities for my first visit? Is the Mexican dialect the same for the majority of cities in Mexico? (would want to practice) At may age, will private health insurance be available? I read conflicting information and find some countries will not sell past a specific age. And need to understand the plumbing issues in the larger cities such as flushable toilets (yes, this is important to me but did experience bidets in Spain) Any suggestions as to where to begin? Looking forward to learning “updated” information and have learned a lot from YouTubers as well.