Some nationalities can get 90 days on entry.
Andorra, Argentina, Armenia, Australia, Austria, Barbados, Belgium, Bolivia, Brazil, Bulgaria, Canada, Chile, Colombia, Costa Rica, Croatia, Czech, Cyprus, Denmark, Dominican Republic, Ecuador, El Salvador, Estonia, Finland, France, Germany, Greece, Grenada, Guatemala, Guyana, Haiti, Hong Kong, Honduras, Hungary, Ireland, Iceland, Israel, Italy, Jamaica, Japan, Kazakhstan, Latvia, Liechtenstein, Lithuania, Luxembourg, Macao, Macedonia, Malaysia, Malta, Mexico, Monaco, Montenegro, Netherlands, New Zealand, Nicaragua, Norway, Panama, Paraguay, Peru, Poland, Portugal, Puerto Rico, Romania, Russian, Saint Kitts and Nevis, Saint Vincent and the Grenadines, San Marino, Santa Lucia, Serbia, Singapore, Slovenia, Slovakia, South Africa, South Korea, Spain, Sweden, Suriname, Switzerland, Thailand, Trinidad and Tobago, Turkey, UK, Ukraine, Uruguay, U.S.A., Vatican and Venezuela.
If you are Australian or Canadian you will need to pay the "Reciprocity Fee". US$100 for Australians and Canadians. You can pay it online before arriving then show them the print out.
Everyone else needs to apply for a visa in advance.
Argentina visa information