I have been going to Los Algodones for years buying prescription drugs. It's the exit you take for the Quechan Casino. Just go south on Andrade Rd almost to the end. Before you get to the border there is Quechan Indian Reservation Parking. Turn right into the parking lot and pay $6 to park. DO NOT PARK IN THE CASINO PARKING LOT. It would take you over an hour to walk to the border from there. The Indian reservations parking lot is close but not past the U.S. Customs buildings. Look for PARKING signs.
Easy walk on a ramp down to the sidewalk that leads you to Mexico. Once over the border smile and tell the nice guys trying to get you to go to a Dentist, Pharmacy, etc, thank you but you are meeting someone there for lunch. The purple pharmacy is my last resort pharmacy, if the cheaper ones don't have what I want, I go there but most have everything or can get it. Go to the square on Calle 2 just after the purple buildings and ask other American/Canadians, where they go for their prescription drugs/Dentist/Eyeglasses. I go to the "Grupo Americano Drug store. It is 2 doors east of the restaurant "El Paraiso" almost to Alamo Alley.
I have never gotten a fake prescription drug nor have I ever heard of any in Algodones. I have even bought generic drugs that are fine. Customs allows me to bring antibiotics viagra cialis to name just a few, without a prescription. They will only allow you to bring over a 90 day supply. You bring too much over the border and customs will question it. So you can get prescription drugs but not Controlled Substances. No vicoden, no cipro 500s, no steroids. C-Ya