Did you know how difficult it is to do a tourist bus tour across the city? No? I tell you, it took me two days to try, after that I surrendered...
1) Saturday 4pm: We are waiting for the yellow citybus to come, tickets can be bought on the bus (according to the homepage). Bus arrives 20 min later: They don't have any tickets, but we can buy them in the official shop 4 blocks from the stop.
2) Saturday 5:30pm: It was not 4 blocks, we walked for 1 hour to find the shop in a shopping mall. But: the shop was closed. So instead, Japanese garden and coffee, next day next try.

3) Sunday, 10.30am: We are more clever, now we have tickets printed from
online. We arrive at the bus stop: First bus comes at 11.40pm. Ok, time
for a coffee.
4) Sunday 12:00pm: We drove 4 stops with the bus,
then it stops. We are supposed to wait 30 minutes, because in front of
us is another bus waiting. So we (thought we) were clever, got off and tried to
get on the other bus to continue earlier. Bis mistake!
a) there was a
queue of 30 people, b) the guide didn't accept our online prints, and
told us to change the tickets at the shop to 'real tickets', c) the lady
in the shop put 2:40pm on our tickets, d) now the guide in the bus
didn't accept us anymore, cause the tickets were only valid from 2.40pm
onwards.
Bad luck, so we went by foot to explore the city. Good luck, we discovered a Brazilian festival with delicious food.
5)
Sunday, 4:00pm: After exploring beautiful San Telmo, we finally caught
the bus to go to La Boca. This area is one of the most beautiful
scenes, but very dangerous. This is the only reason I wanted to take
this city bus, to make nice pictures from a save distance.
6)
Sunday, 4:30pm: The bus turns left, and skips La Boca - it is Sunday,
there is a soccer match, since it is too dangerous/ crowded to go. So I
returned to my home and give up. Next time, I will walk to La Boca...