People on this site can be very helpful, but often are easily distracted and end up getting you lost in the tall grass. If you are here for 2 months you will be on your tourist visa so you won't have, can't get, a DNI,
Don't put more than about $100 pesos on it and you will have enough for about a week of subte or colectivo rides and you won't be out enough to get to exercised if you lose it. I bought my card at a western union office and charged it once at a Kiosko and again at the subte station.
When you go to use the card on the subte there is a card sized place on the turnstile right under a small screen. Lay your card on the place and hold it down until your card is read and the screen says PASE, then push through. In Atlanta our transit card simply needs to be tapped, so I wasted several peoples' time and patience learning how they do it here.
When you go to use it on a bus, colectivo, when you board the driver will mutter something unintelligible to you and me. He is asking for your destination so he can know how much the charge is. Answer with the name of the cross street or subte estacion you are going nearest to, then on a yellow box in front or just behind the driver a little screen will flash the fare. Usually 3.00 to 3.50 (20 to 30 cents US more or less, so don't worry about it). Below the screen on the yellow box is where you press your card, again until it's read and flashes your new balance.
The inter active website http://www.omnilineas.com/argentina/buenos-aires/city-bus/ is very helpful for planning your trip on colectivos.
The google map of Buenos Aires https://www.google.com.ar/maps/@-34.6158238,-58.4332985,12z?hl=en is good in that it shows stores, restaurants and places on interest on your map, and will find something if you type it in. It will also give you directions. It will help you with subte routes, but not colectivos.
Finally the governments interactive map is also very fine and has good direction finding features, for walking, subte and colectivo. It's only drawback is that it doesn't show places of interest, restaurants, etc. It is at: https://mapa.buenosaires.gob.ar/comollego/?lat=-34.620000&lng=-58.440000&zl=12&modo=transporte
In addition to these resources you can buy a Guia T at any Kiosco or news stand. It has all of the colectivo routes on a page by page map of Buenos Aires. It can be tough to follow sometimes, but if you don't have a phone with a Guia T or Mapa de Buenos Aires app, it can come in handy.
Also, be sure to make use of your smart phones gps and mapping features. It can keep you from straying too far off your path. When you are tired of walking, or need to get your bearings, there is likely to be a cafe/bar on the next corner where you can sit relax and have a coffee or beer and figure out where you want to go next. This is a wonderful city for just wandering around in on foot or on colectivo.
Last but not least, if you are lost and/or exhausted and don't wanna fight it anymore, just flag down a taxi, it costs way more than a bus or subte ride, but you are still not likely to spend more than $5 or $6 dollars US. Chill.
Enjoy the colectivos; the subte is faster, but the view generally sucks. Have a wonderful time.
p.s. When you get off the subte and climb up to the surface and look around to get your bearings, remember, the sun in to the NORTH!
