I think the OP should, after seeing a Mexican physician to re-evalueate the situation, do some serious shopping for generic equivalents at the many discount 'farmacias'. In many cases, there are generics available at 1/2 to 1/5 the cost of proprietary medications. Also, there are older medications which are just as effective as the newer ones 'pushed' by the pharmaceutical reps.

Cheldear,
Your prescription is not valid in Mexico, but it may be informative. Be sure the writing is legible and ask the 'farmacia' to look up the medication. Proprietary names aren't necessarily the same, as there may be other manufacturers of the medication.
In Mexico, only controlled substances (narcotics) require a prescription. However, there is talk of some antibiotics, which are often over-used, requiring a prescription in the very near future.