Some nationalities can get 90 days on entry.
Andorra, Argentina, Armenia, Australia, Austria, Barbados, Belgium, Bolivia, Brazil, Bulgaria, Canada, Colombia, Costa Rica, Croatia, Czech Rep, Chile, Cyprus, Denmark, Dominican Republic, Ecuador, El Salvador, Estonia, Finland, France, Germany, Greece, Guatemala, Guyana, Haiti, Hong Kong (S.A.R.), Honduras, Holy See, Hungary, Ireland, Island, Israel, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Macedonia, Malta, Mexico, Monaco, Montenegro, Netherlands, New Zealand, Nicaragua, Norway, Panama, Paraguay, Peru, Poland, Portugal, Puerto Rico, Romania, Russian Federation, Saint Kitts and Nevis, Saint Vincent and the Grenadines, San Marino, Santa Lucia, Serbia, Singapore, Slovenia, Slovakia, South Africa, South Korea, Spain, Sweden, Switzerland, Thailand, Trinidad and Tobago, Turkey, UK, Uruguay and U.S.A.
Granada, Hong Kong (with BN passport), Jamaica, Malaysia and Venezuela are permitted to stay for 30 days.
If you are Australian, Canadian or from the USA you will need to pay the "Reciprocity Fee". US$160 for USA, 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
The official visa information (In Spanish)