Northern Mexico is super dangerous so realistically you would have to fly. And I don't think the TSA will like you carrying a multi year supply of meds back to US

I live in Tijuana and it's actually not super dangerous unless you go to a bad neighborhood. Sure, relatively statistically speaking, there is a higher chance of something bad happening. But it is still a very tiny chance if you stay within nice neighborhoods and are just trying to buy medication. By the way, unfortunately the only part that of Tijuana that a lot of Americans see is the one designated for maximum debauchery and is one of the worst neighborhoods.

The pharmacies right by the border are fine, but if you want a nicer area, walk across the PedWest crossing and stand in the Uber waiting area for an Uber to go to Playas. Then you can go somewhere like Farmacias Roma or Farmacias del Ahorro or a bunch of other nice stores with people wearing lab coats. You could also just go to Walmart for medication if you want but recently they seem to be missing basic things I needed so they probably aren't the best.

This morning I drove town to Tijuana and bought my "refill" from Farmacia Roma 3 blocks from the border for $15. My US doctor wanted to charge me $200 for additional tests and then $30 for the same meds. This is for a simple bacterial infection.

Border towns might be a decent idea. I was only considering crossing northern Mexico by car which natives visiting the US have told me is something they never do.

Well I would not want to drive in TJ because the signs are in a different language, people drive differently, giant potholes, other issues.