I've purchased most every type of pharmaceutical manufactured while shopping in Tijuana. I've NEVER been asked for any type of documentation when crossing back into the U.S. on foot or by car. The standard fee is $20 for two scripts. Just fork over the cash and the doctor writes the scripts. Doctors with offices in the Santa Teresa Plaza (?) near the arch are the easiest to locate and keep most meds in their offices - no need to go to the farmacia. If you phone ahead, the doctor will have the meds waiting for you and an assistant will take your dollars.