Originally Posted by
BamaVol
I believe a US citizen can visit Argentina a lot longer than a weekend without a visa. Offhand, I think it was 6 months. You'll be given a form upon entry. You fill it out, they take half, you pay US$18 and turn the other half in when you leave. No visa, but bring your passport.
Just to clarify, you don't pay anything to enter the country. The US$18 fee is a departure tax that every passenger must pay at the airport when leaving.