I'd be really careful in TJ - we went to Ensenada for a weekend last year. I looked up all these sites about traveling in Baja. Several of them had posts addressing Americans purchasing medications there (not just pain meds). One poster wrote that some of the farmacias will call police if someone is trying to buy meds w/o a valid script - you get outside and there are Federales waiting for you. Not a pleasant idea, so I didn't even try. Small amounts, maybe, but I'd take empty bottles of the same meds with you and dump the pills in there. At least they're from a US pharmacy with your name on them. My aunt and uncle have a place in Rosarita and they take their US scripts and have them filled there but keep a copy of the script to show Customs if necessary.