From the Internet:
Argentina, for much of its history and including the present day, has been an overwhelmingly Roman Catholic country. The historical background is very much due to the Spanish influence brought about through the newly conquered territories. However, immigration throughout the 20th century has brought other Catholics and denominations from various regions to Argentina. Overall, 24% attended religious services regularly. A recent study found that approximately 11% of Argentines are non-religious, including those who believe in God, though not religion, agnostics (4%) and atheists (5%).
Estimates for the number of Roman Catholics vary from 70% of the population, to as much as 90%. The CIA Factbook lists 92% of the country is Catholic, but only 20% are practicing regularly or weekly at a church service.
So, it is like Mexico: NOMINALLY Catholic.