76 born in Greece - Argentina, Capital Federal Census 1855
FamilySearch.org has a FREE database titled ARGENTINA, CAPITAL FEDERAL, CENSUS 1855 - there are 76 people listed as being born in Greece. You will be able to see the actual Census page - example above.
Keep in mind that names have been changed or are in Spanish - for instance Juan Jorge - is this Ioannis Georgios (John George) - he is listed as being born in Greece. He is 70 years old in 1855 and has been living in Argentina for 30 years.