First, I think if you all are earning $6000 USD per month for a family of three, you will have little or no problems living here in decent style. In fact, per person, your husband would be bringing in a bit more than I do for my family. For the $4k not paid in white - depends on how they give the money to your husband, whether it's deposited in a bank back in Brasil or cash in hand here. Currently, it is somewhat of a problem to get money into the country, but hopefully that will change with Macri before too long. A lot of us expats have to deal with getting the money in - it's possible, it's just that one spends an inordinate amount of time worrying about such things. And many of the (at least, easier) mechanisms for doing that are located in the city itself.
I estimate that we spend about $2200 to $2800 pesos per person at the supermarket per month. I live in Recoleta, which is an expensive place, and you may well find that outside the city the prices are a bit more reasonable than that. That would include supplies as well as food, BTW.
I haven't driven for around a year (my license expired, but I'm working on that), so I haven't really looked at gas prices lately, but I'm thinking they're in the neighborhood of $14 pesos a liter?
I used to live out near Garin, which is about 38 kilometers outside the city, about 10 kilometers closer to the city than Pilar on the same highway. Fortunately, I work at home and didn't have to drive in every day for work and when I did, it was at a time of my choosing. The problem used to be (it's been some 5-6 years since I lived out there so things may have changed, but I doubt it for the better) that the traffic going in in the morning and coming out in the evening was absolutely horrible. Horrendous. We're talking about 20-25 kilometers of bumper-to-bumper traffic sometimes, moving very slowly. Not to mention the toll booth you have to go through coming and going, at something around $20 pesos a trip now, I believe. The problem is there's only one real route to take from out there to and from the city and everyone that lives out there must take it. Unless you take the train, which even my wife, who is from Paraguay and used to dodgy things such as poorly maintained train stations, refused to take. unless she could come and go during the day.
I lived in a closed neighborhood out there and didn't like the way the people there treated my family, they being Paraguayan. Most of the people that live in closed neighborhoods out there are of the "upper class" and they have some ways at looking down their noses at certain people. We didn't have any real problems, just felt shunned (and we heard gossip from all of the Paraguayan maids that worked in these people's houses, who my wife befriended, how they felt about us, supposedly). But we were surrounded by open middle class neighborhoods and many nice people outside the walls of our barrio cerrado. Many of those homes looked to be fine dwellings, though many were surrounded by walls (there are also neighborhoods like villas, or slums, very nearby as well, but i don't think you can completely get away from that as far as I've seen).
Pilar is a pretty nice place, I think. I always enjoyed going up there from where we lived. There's a Jumbo/Easy (Jumbo is a big supermarket, Easy a big hardware store) in a shopping mall with lots of nice shops and restaurants. There used to be a good Mexican restaurant right across the street form the mall, and a really, really good Italian place a few blocks away. Good prices on clothing compared to the city, but still low-quality stuff for the most part.
If I had to commute into the city of BA, though, I think I would have gone mad. And this from a person who used to drive across Houston (freeways always under construction and horrible traffic!) every day to get to work in the 80s and 90s.
You might also look at places like Olivos or Vicente Lopez, just outside the city, much much closer than Pilar (and certainly than Mercedes) on good train lines, not as hard to drive in from or leave the city to (although there is still traffic, sometimes really bad - just not as far) and has some pretty nice living places as well. Even along the highway (Panamericana) that leads out to branch to Tigre, Pilar and Escobar (another decent little place), where it leaves the city is not too bad, for being close-in.
One other thing you might think about - I regret that we didn't stay out in the suburbs if nothing more than for the kids. We have 19, 17 and 15 year old girls (sisters of my wife who came to live with us starting some 8 years ago) and the lifestyle between people out in the far suburbs and here in the city, as far as what kids are allowed to do, is way different. I'm not sure how Olivos and Vicente Lopez are in respect to this, but I think you're making a good move to stay outside the city and not bring your 15-year-old into at least parts of the BA city proper, where kids routinely start partying around 1am and wander the streets at all hours of the wee hours and into the mornings, sometimes even on weekdays. it's a constant fight for us to keep our girls reigned in as teenagers only see what their friends do, not what's good for them
