I ride my bike everyday. It’s actually CHEAPER than the super cheap public transportation system, and usually faster (in two months you can EASILY save the 200 pesos it cost to buy you a used bike).
That being said if you don’t feel safe as an urban US cycler, you won’t feel safe as a BA cyclist. The League of American Bicyclists recommends you stay in the rightmost lane that serves your destination for good reasons. But here, that is nearly suicide with the colectivos and people coming in and out of taxis. The left lane, particularly on avenidas is the safest and usually where the carril for bikes is painted. The new bici-sendas can be a blessing and a curse, gives an illusion of safety and a clear path but is also a sure easy target for bike robbers, littered with glass and trash and unaware pedestrians that step out in front of you. Keep in mind many times at intersections, cars don’t stop.
But I actually think you are SAFER here biking because motorists, even though they drive like crazy people in appearance, are used to crazy things happening on the road. They are way more attentive than US motorists and EXPECT A LOT OF bicyclists on the road. Sadly, a lot of cyclist deaths where I’m from happen from cyclists hit from behind on a main artery road by distracted drivers, not expecting anything but concretes, strip malls, and other cars.
But my tip is to bring your old US urban bike locks and some nice bright tail lights (which everyone has here but you can get brighter ones by the great folks at Planet Bike, for example). Those locks are much harder for the chorros to cut here, you even see them still dangling on polls all over the city. Locks here that are decent are expensive and are really not all that great, so buy a cheap bike and lock it with a nice old (old looking) lock from home. My boyfriend’s heavy duty chain lock got cut through and his bike stolen, but mine is still holding strong!
