In Mexico City, most offices are open from 9 AM to 5 PM or even 7 PM, Monday to Friday. Some banks have extended hours in some branches. Also they may not open on Sunday. The standard working schedule in the shop is Monday to Friday, eight hours a day and half day Saturday. Mexican business people wear suits, so they expect you to do the same, no matter how hot the weather.
Shorts are a no-no.
Not even for a picnic. If you are invited to a picnic or a tour of the country side, dress casually, but elegantly. Polo style shirts, a sweater and sporty slacks would do. The Art of Negotiating Learning to negotiate in Mexico is key for your business success. In Mexico it is impolite to verbally disappoint you.