I will add that Tijuana is the murder capital of the world right now. Mostly confined to cartel members, but....and it's a big BUT....
Going down there with a lot of cash to a pharmacy might have someone tip off a cartel member/street criminal for a robbery. If they know you're coming, they'll steal the cash when you arrive at the pharmacy. Leave the pharmacy and they will rob you of the HGH, bring it back to the pharmacy, who will pay a discounted rate to buy it back and will keep the excess cash. Taxi drivers are a potential tipoff source as well.
So....I would advise against this unless you know someone who can vouch for a particular pharmacy in advance. It's not like the old days at all. I am very up on crime and cartel activity down there (Borderland Beat is a good aggregate source of news, but there are so many stories that they are only reporting a small percentage of them), but everything along the border is just GOING OFF right now due to cartels battling for control. Still....Americans not involved in the drug trade are still fairly hands-off for the cartels as they don't want the increased attention that will bring. Robbing Americans? No problem. Killing them? Off the table if you're not doing business with the cartels. Someone kills an American, the cartels are likely to kill the killer. That could change. Things are rapidly worsening due to AMLO's "hugs not bullets" policy. He is in the pocket of the cartels.