Moderate Climate Locations

I would suggest investigating the colonial highlands.  For big cities, Mexico CIty, Guadalajara, Puebla. For smaller cities, Guanajuato, Queretaro, San MIguel de Allenda.

And a little more moderate and less cool, Lake Chapala

How about communities with  altitudes of  1000m or less......

I have never been there but Oaxaca City has always intrigued me and I think it may have moderate weather. San Miguel and Chapala are good choices but on the expensive side.

Oaxaca is hot.   I live in San Miguel and don't  find it expensive at all.  I know many people living a nice life for 12 to 1500 a month.  San Miguel is awesome!

I just found weatherspark.com. It is a good way to compare climates between two places. It has great graphic charts that make comparing easy vs tables of numbers. I'd pick an area you're familiar with, then compare it with various Mexican cities.