I live in Buenos Aires and is mostly a safe city but you should take into consideration most of the usual security measures / recommendations as in any big city.
First recommendation is look like a "porteño" -> (porteño = people that lives in Capital Federal), don´t show off, leave your valuable objects out of the view and visit places where people goes and look like a local and go where the locals
People here is friendly with turism.Take into consideration some speak english but mainly spanish (local language) but they will effort to help you
Public transport is good in Capital Federal, take into consideration to get a Sube card. It´s a card to use buses, train and subway. You should be a local to get one and it need to be charged previously but there are several kiosks that sell it charged. Just ask "donde puedo comprar una tarjeta sube?"
Also you have Uber (but there is some controversy here about them with taxi drivers) so, mostly taxis. Are expensive but if you are not in a budget simplify your life a lot.
Regarding taxi use, take into consideration they prefer ARS (pesos argentinos). Being turist, don´t go with the street ones in order not to be cheated (unfortunately there are good and the other kind of drivers who sometimes try to cheat turists...) -> I recommend you to get maybe a local chip for your phone for calling a radio taxi for example one big is named Premium (more secure) or ask for them in the front desk of your hotel / place.
When arrive to Ezeiza or Aeroparque, be prepared to be charged more than the usual price (it happens all around the work). Don´t go with the ones outside... It´s better to ask in the counters inside for a taxi / remise in ARS (pesos argentinos), and you´ll be fine. In my opinion is not good to call Uber there because taxi drivers there could cause you problems.
Im Capital Federal there are some bicisendas and the goverment offers some free bikes to go around the city but you have to let your passport / ID, so, think about it. Maybe you can find some place that rent bikes or offer guided bike tours instead. Be careful with traffic in Capital Federal.
Take care when exchanging your money. Do not exchange money at the airport (just the necesary) an NEVER in the streets... do it in banks -I don´t know if banks exchange to turists- or "casas de cambio" only. They are mostly anywhere in the city (mostly in Microcentro during the week and only during the day)
Credit cards are accepted in most stablished places but you need some change in order to move because not all the shops / places accept them. Carry with you minumum ARS 1000 / 1500 with some change for some cases (USD 70 / USD 100).
Exchange rate aprox.: 1 us dollar = aprox ARS 15 pesos argentinos. If you have euros = the same recommendation obviuosly but for people here is most common deal with US dollars
For you to know, I will put the word "day" on the places you can go better in that time of the day and "night" or / and "day / night" according my experience and where is nicer / safer to go / stay, of course "s.h.i.t. happens", but don´t be afraid... as in any place in the world just be cautious when your gut tells don´t stay / go to that place...:
if you are thinking visiting Capìtal Federal there are many places to visit:
Ask for a kiosk where they can provide turism information where you can know more about Buenos Aires and local atractions.
Palermo -day / night- pubs, restaurantes, nightlife. Shops during day, planetario, hotels / hostels greenlife,walk, bike rental, artificial lake, Hipodromo (horse racing), even if you don´t gamble is a nice place to visit
Belgrano day / night: shops during day, restaurantes, cafes,
San Telmo have restaurants, shops selling historic stuff, hostels (If I were turist I woul not stay there -but just because of my "taste"), ferias and walking during the day and there are some movement / shows also during weekends- day / night -but only night some days, not a nice place to stay when there´s nobody around-
Puerto Madero -day / night- Restaurantes, pubs, cafes, riverside, protected by Prefectura (river police)
Costanera: riverside -day / night- Restaurantes, carritos to eat some sandwiches "al paso" (during day)
Recoleta -day / night- pubs, restaurantes, nightlife, shops
Barrio Norte -day / night- pubs, restaurantes, Shopping, shops
Nuñez -day- - there you have River Plate stadium if you want to watch a match -mostly sundays- and better location than La Boca
La Boca -day- -Caminito, La Bombonera -Boca Jrs Stadium-, etc someone said this is THE place to go to watch a soccer match, but I don´t like that part of the city for a turist to go alone, even the atmosphere inside the stadium is rare in my opinion, but maybe you can find a guided tour and it´s a really nice thing to do and you´ll find how "La Bombonera late"
Calle Corrientes -day. has some theaters and restaurantes (pizza al paso, asado, etc).
Also in downtown -day- you can visit el Congreso, Casa Rosada, Obelisco, Catedral, some historical places. Mainly to go during day.
I prefer downtown during day, when people is there. I don´t like downtime at night the atmosphere changes a lot during weekdays and you have to know where go (in case would like to go at night find a local to go with you and better during weekends)
Also sarch for a tour day -search for Buenos Aires Bus, it has 24 stops fot you to visit some distinctive places from Capital Federal / downtown- it´s paid bus without roof but looks niche for turism and you can visit every stop
For renting or hotel I would recommend stay away from downtown (again I don´t like it at night). Better go to Palermo, there you have a lot of youth, nightlife, restaurants, pubs, discos and is well located.
Puerto Madero is also a nice place to stay and very well located and secure but less variety and expensive (I don´t know what´s your budget) but you can find some nice places and more expensive hotels. There you have HIlton, Faena, etc. but also some places in Airbnb.
Take into consideration that here in Buenos Aires we are some like "owls" and there is a lot of nightlife (even during some days of the week) you´ll find restaurantes and cafes opened late at night
If you want to visit places in Buenos Aires but outside Capital Federal, go to north. There you have cities like San Isidro, Olivos, Martinez, places to go out, drink / eat and the river + river sports + Shoppings even in San Isidro you have el Hipodromo (horse racing), even if you don´t gamble is a nice place to visit.
For reaching those places you have public transport -I recommend el Tren de la Costa- which is nice to stop by some stations and walk (during the day and mostly weekends) but is also ok to go in car during day / night because of the distances.
Regarding WiFi (fundamental topic!), you´ll find that most of the cafes / restaurantes give complimentary access. In case it´s rotected, just aks for the SID / password... Even there is open signal in some squares (anyway don´t go over there showing your phone) lol
I heard Buenos Aires is some kind of expensive destination for tourists, but for sure you´ll love it! You´ll find places to visit, many people to meet and also fun!
Wow! hope my recommendations will make your trip even better. Any other question, plase let me know and I will do my best to help
Have a nice trip!