Just like nowhere in the US is perfectly safe. I've driven all over Mexico, seen the country at its worst and best over the last 40 years. I've lived in Mexico for several stints after my mission for work, mainly in Mexico City and Monterrey. I don't think there is a beach worth visiting that I haven't at least driven past. I've helped several people setup the legal entities necessary for US residents to sort of own property (sort of, because it technically can be confiscated at any time if you're not a Mexican citizen).
My mission was based in Guadalajara, so I'm very familiar with the retirement communities, I've been back several times over the years to visit friends there.
Chapala and Ajijic can be safe places if you:
- Drive a beat up car that is a little dirty all the time
- Never draw attention to yourself while going to the bank, post office, etc. (especially, never let the local bank staff know what your assets are outside of Mexico and keep very little in Mexican banks)
- Act like everyone is watching you to see what they can steal from your car, your house, etc.
- NEVER call the police for anything, no matter how grave the crime