Contact Spencer McMullen, an attorney in Chapala. I had a visit with him today about my Mexican Moto drivers license and he mentioned he is planning to sell his Honda XR125, Jalisco plates and in like new condition. He is from California and speaks perfect English if that is an issue, here is his contact info:
I think this is the bike he has:
Personally, I like the Tornado 250 better, but it costs more than twice as the XR125. You will need Mexican liability insurance 300k liability, and that may cost you 2000p a year, not sure for this bike. Don't buy a Chinese scooter. If you want new, Chavane Suzuki in Guadalajara has a good selection of 125s and they are affordable and bulletproof.
Permanente visa is a no brainer, one time and you are done. Temporal visas may cost you about 4000p each and are renewed annually.