Mexicans are quite status conscious and successful people are expected to look successful. Dress is, therefore, of great importance and it is vital to look smart in both business and social situations.
Business dress in Mexico City tends to be somewhat more formal than in other parts of the country. Suits are often worn in the capital whereas smart shirts and slacks are sufficient in the provincesIf in doubt, check in advance.
Remember that Mexico is hot - so take lightweight clothing.