Gato,
When you're on Benito Juarez (Like coming FROM the Old Port), Go through the stoplight of Calle 13, and continue on benito juarez, to the next stoplight, turn right at this stoplight, at the big discount store called "AKA SI", once you turn right, continue straight on that road (Melchor Ocampo), you will see a paint store on the right hand side called Techos Paredes, the next block I believe, on the LEFT side theres a big green pharmacy called "Botica Lux", well, the "Optica Turati" eyeglass store, is in the next building after the pharmacy. It's a little yellow building. In the store there are 2 english speaking employees, Gustavo Turati (owner of the store), and Carlos Garcia (front desk). Gustavo will take care of you and will work with you on the prices. Many many many people come from the states to have Gustavo do their eyeglass repairs and fittings because hes really the best in Penasco and he works with you on the prices.
Hope I helped!