It is better to ask for a tourist visa!

This Info was checked on the Cancilleria (Ministry of Foreign Relations)

1) Countries that require tourist visa to enter Argentina:

http://www.mrecic.gov.ar/portal/temas_consulares/visas.html

Most countries don't require visas, but China and India do require visa.

2) Requirements for a tourist visa:

http://www.mrecic.gov.ar/portal/temas_consulares/visas_turismo.html

• Valid passport,
• Form provided by the consulate,
• Photo (4cm by 4cm),
• Round-trip Ticket,
• Payment of consulate fee,
• Show that you have economic means for this stay.

The tourist visa is valid for 90 days.

American citizens don't need visas for Argentina.
Nationals of the following countries do not require a visa when entering Argentina as a tourist:
Andorra, Austria, Australia, Barbados, Belgium, Bulgaria, Bolivia, Brazil, Canada,
Switzerland, Chile, Colombia, Costa Rica, Germany, Denmark, Dominican Republic,
Ecuador, Spain, Finland, France, United Kingdom, Grenada, Gibraltar, Greece,
Guatemala, Guyana, Honduras, Croatia, Haiti, Hungary, Ireland, Israel, Iceland,
Italy, Japan, North Korea, South Korea, Saint Lucia, Liechtenstein, Luxembourg,
Monaco, Former Yugoslav Republic of Macedonia, Malta, Mexico, Nicaragua,
Netherlands, Norway, New Zealand, Panama, Peru, Paraguay, Romania, Sweden,
Singapore, San Marino, El Salvador, East Timor, Turkey, Trinidad and Tobago, United
States, Uruguay, Vatican City, Saint Vincent and the Grenadines, Venezuela, South
Africa.

It is better to ask for a tourist visa!