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Business Customs As in many countries, entrepreneurs intending to successfully do business in Argentina should take the time to develop a close personal relationship with their agent, representative, distributor or other business partner, and maintain it with regular visits. Argentine customs are generally more formal compared to those in the United States or Europe. Business dress, appearance and general approach and demeanor should be conservative. Politeness is very important, and efforts to rush a business deal will unlikely be met with success. To establish trust, time spent on social activities is fundamental to developing a solid business relationship.
 
It is important to shake hands with everyone in the room upon arriving and leaving, and with women, it is customary to kiss once on the right cheek, or shake hands. Contacts and introductions are important, therefore use the services of organizations such as the American Chamber of Commerce, industry associations, or other contacts, as opposed to the direct "cold call" approach. It is important to be prompt to business meetings, and always have a pre-arranged appointment. Be sure to have an ample supply of business cards. It is beneficial to have cards printed in Spanish as well as English, although not necessary.
One cultural consideration U.S. travelers should note is that the term "American" denotes someone from the Americas, North or South, not just from U.S. Saying you are from the United States (los Estados Unidos) is clearer.

Currency
The Argentine currency is the peso, and is signified by the same symbol $, as the U.S. dollar. Automatic tellers are widely available in Buenos Aires, allowing travelers with a variety of credit or debit cards to withdraw funds automatically in local currency. Many automatic tellers even provide the option of withdrawing U.S. currency. Note that in some locations paying with travelers checks may not be accepted. Prices in Buenos Aires are comparable to large U.S. cities for hotels, restaurants and related travel expenses.

Language
Spanish is the national language of Argentina, but many business people speak English, and other European languages as well. However, do not assume that your contacts will speak English. For U.S. business people who speak Spanish, note that the Argentine version of Spanish has distinct differences in pronunciation, cadence and vocabulary. All business in Argentina is transacted in Spanish, and all documents and records must be in Spanish to constitute valid evidence. A certified public translator should translate business documents in a foreign language to be presented for legal purposes to Argentine authorities.

Time
Argentina is three hours behind Greenwich Mean Time, and two hours ahead of Eastern Standard Time. Argentina does not have daylight saving time changes. Therefore, the time difference with Eastern Standard Time is one hour, but with Eastern Daylight Time it is two hours. The 24-hour system is generally used rather than the 12-hour a.m./p.m. system. For example: 3:00 p.m. is referred to as 15:00 hours. Business office hours are generally Monday to Friday from 9:00 a.m. to 6:00 p.m. (two hours early for factories) with one-hour lunch break. Work luncheons are frequent for business executives and they generally extend from 1:00 to 3:00 p.m. Business dinners, and dinners in general, do not begin until 9:00 or 10:00 p.m., therefore it is common to return home or to the hotel to sleep for few hours before going out. Because evenings start late and end late, the early evening nap is the secret to being functional the next day. It is advisable to not schedule morning meetings before 10:00 a.m. Business breakfasts are not so common.

used source: 
U.S. Department of State: FY 2000 Country Commercial Guide Argentina