you can get it. A little hassle but if you do reaserch prior, get a LEGIT mexican sript and also have a US backup you will be fine.
Not as easy as just getting 30 valiums but sure its their, wherever their is money to be made its their. If you get scripts then they can do nothing and will do nothing since they know what kinda trouble they can get into for trying to get to you with a legit script. Now if not then they have legroom but if you your docs (script etc.. ) you will be ok.
Just do your researh prior and even phone the doc/pharm prior to comming and let them know you have your presciptions.