Mexico can do amazing things with vehicle repair, high pressure hoses can be rebuilt, compressors can be rebuilt... pretty much anything can be rebuilt, at a fraction of the "replacement" costs we have grown so accustomed to in the US.
If you're planning on staying for a bit, I'd recommend you look for a solid "general mechanic" shop, were you'll do most of your wrenching, and ask them to recommend you go a solid AC repair shop.
Sometimes folks will wrench a little bit on everything, but will not really know the ins-and-outs in a particularly mechanical discipline.
I'd rather take my vehicle for "specialists" treatment, for certain things... i.e., transmission, electrics, and AC.
Everything else is handled by my general mechanic, or "mecanico general."