Most of the porteños are friendly, I don't know what is it with the "attitude" thing, but since I was born HERE I've never had that problem (and my parents are not from Argentina). Obviously, there are certain exceptions, but that's totally normal.
I'm eager to meet people from all around the globe and learn about their cultures, traditions and way of living (so are most of my friends). But from my point of view, there is a common belief that porteños are unfriendly, selfish, unhelpful and so on and that's the main issue why it's hard to make real friends, because nearly all of us have prejudices . I believe that a reduced number of individuals shouldn't reflect what the society really is like.
I certainly don't believe that the length of your stay determine whether you're "worth" someone's friendship or not. That's really f*cked up, and to be honest, I've never heard that before. Even if porteños can't speak english, they'd try to help you out (it's hard to find a porteño that speaks ZERO english nowadays, c'mon).
Olivos is a beautiful place to live, and like everyone said, it's just a 20 minute ride from the city centre, and the train that takes you there is the safest one so far (Línea Mitre, Retiro-Tigre). Also, there's buses too (29, 152) that you'll eventually learn how to take. Public transport, luckily, is super cheap in Buenos Aires (not taxis though...).
I don't know why is that everyone thinks that porteños are like "mean creatures" that are super hostile, desperately wanting to scam you or whatever their minds can imagine. It is certainly not like that and you'll find plenty of opportunities to meet really nice people who you'll eventually make friends with, wherever you are. That doesn't mean that you should talk to everyone on the street and trusting everyone or anything like that, of course you've got to be cautious, like in any other country.
Hopefully you'll be able to enjoy and get the most out of the city of Buenos Aires while meeting nice people, and who knows, you might end up loving it here.
If there's anything you need just let me know, I'll be glad to help!
Best regards,
Fernando