Right of San Martin is pedestrian street. On both sides take turns various shops which sell a stuff of good quality. In the front of shops, the tradesmen invite you to go in their shop. 'I have your number!' was the most often repeated sentence I heard on the streets of Buenos Aires.
In late night the crush of cabs wont vanish. The traffic flows without any hurry. The hack drivers are not annoying and don't bother you at walk, but I cant say a same for beggar children and dealers.
If you didn't see a lot of garbage over a day, your impression will change over the night. All of rubbish of Buenos Aires is fold together at the evening but disappears over the night. Don't be surprised if you find a street looked as a big truck of rubbish is overturned around. The garbage is picked every night and the streets become clear before early morning.
A short walk over streets of Buenos Aires is a discovery of thousands of different sights. From obelisk with a no end of cars running by, you can turn on any of hundreds of small streets and you'll see a different picture. On fronts of old houses hang a millions of advertisements which don't disappear neither when you turn around a corner down from the main street. If you are not familiar with the crush of big towns, you will maybe feel nastily when big busses run a span near your shoulder. In any case it is good to be careful.
In tight streets the sun light slowly disappears and a traffic becomes noisy and bothering. This continues in a late night. If you are logged near road and you like to sleep at the opened window, you'll have a bad slumber.