Argentina received them for three main reasons
1) The country was neutral during World War 2, like let us say Switzerland
2) They were economic bonds between Argentina and Germany, and this last one provided with a lot of goods to argentina
3) The President of that period in Argentina called Juan Domingo Peron (Evita´s husband) was part of a plan called ODESSA that allowed the entrance of many war criminals in order to give them protection and avoid being judged in Germany
¿Are there still communities?
As the other user said, the Nazis arrived in the 40's and they were in theirs 30, so many of them or almost all of them are dead. And they changed their names and surnames so as not to be discovered and they did form some isolated communities of which not much is left. There are places that are supposed to have recieved Nazis such as Villa General Belgrano, La Cumbrecita, La Falda and mainly in Bariloche and neighbourhood areas. But as they were hidden and with false identities, these are just suppositions of where they could possibly have been.
This is what I know. If i made many mistakes is because I'm from Agentina and I'm learning English. If you understand Spanish there is much information online about Nazis in Argentina.