You comment, we respond. Apparently we never actually told you about the noisy San Cristóbal vehicles. There are, of course, the cars with the megaphones paid to drive around blaring ads, sometimes for political campaigns, sometimes announcing the next Lucha Libre. But these cars generally stay closer to the center and out of our neighborhood.
The noisy trucks we mentioned are important to us now that we are home-renters because they announce utilities: water, gas, and garbage collection. The city water in San Cristóbal, as in much of Latin America, is not for drinking. Instead, you need to buy drinking water in large 5-gallon jugs from the water trucks that drive slowly through the neighborhoods, playing their jingles. Imagine a very loud icecream truck playing Raindrops Keep Falling on my Head with lots of screaming on top (Señora! Señora! Ya llegamos, ya estamos aquí! Con la mejor agua...)
In addition to the water trucks, we also need to listen for the gas truck. The gas we use to heat our water and run our stove comes from two large canisters behind the house. When one is empty we wait to hear a really loud jangly sound outside. The gas truck announces itself by dragging a large chain with iron rings up the cobblestone streets. Some gas companies have also begun playing jingles. We run out, flag them down, they change the gas canisters.
Finally, there is garbage morning. This one really isn't so loud, but falls under the category of "important noises". About five minutes before garbage collection, a man walks up and down the street ringing a bell. Then we take our garbage and line up with our neighbors to pass it to the garbage truck. Garbage morning is something of a minor social event.