It's not for everyone, but there are two spots in Mexico that are great, Lake Chapala, Jalisco state, and the city of Oaxaca, Oaxaca state. There are thousands of U.S. and Canadian retires living around Lake Chapala, mostly in the town of Ajijic, living the good life--on the cheap.
I lived in Oaxaca for a decade, and the running was fantastic (it's a mile high city, and the mountain trails go up from there.) The local running scene is active, and convivial.
Good medical and dental is available, for about 25-30% of US rates. I did a root canal, and hernia surgery, -- but I did pay for that stuff out of pocket. There is a lively expat community in Oaxaca.
I was drafted to play music with a Thursday night jam session, just out of town, on a expat buddy's ranch. He had a mezcal still a few yards from where we played under the stars. OK, a bit too much fun at times, but pure magic.
The trick is to go and stay for a few weeks, and see what you think.
Moved back to the states when the kids hit high school age. Those spoiled brats demanded a return to Cali, and of course we obliged them.