hey i'm new to this board to but I lived in mex on the boarder for 15 years. Just get in a cab and tell the cabbie what your trying to do and he should know where to take you either a doctor that will write a no questions asked perscricption or a pharmacy that sells with out prescriptions or if your cabbie is a pendejo or you don't like what he's telling you the pharmacies a lot of times will have people that speak english looking for Americans in the downtown area to bring to their shops,so that works too. If you think that its too expensive try to barter them down, if they won't budget on it respectfully leave and search for another place, if you disrespectfully leave I can almost guarantee you will searched when you cross back to this side. I hope you can speak spanish because the prices a lower if you do. Good luck