We could not figure out what was going on earlier this week. So I took a video and waited until someone on Uruguay Expats on Facebook posted the explanation.
It seems that the Uruguayan President made a speech and if the citizens do not like what he said they take their pots and pans and go out into the street and bang them around. Then the buses and cars got into the act with horn blowing. This lasted a good 30 minutes, with more and more folks coming out on their balconies and more and more cars and buses joining in.
Caceroleo – is a form of protest in which the protesters make known their discontent by means of dined noise (typically beating pans ), be it at an agreed time in advance or spontaneously. Demonstrators can participate from their own homes and without the need to concentrate on a particular place, peering at windows and balconies or in the antejardins of houses, and rhythmically brandishing the objects they have at hand (commonly pots, pans and other household utensils; Hence its name), thus being able to reach the protest a high degree of adhesion and participation. Like other types of demonstrations, a cacerolazo can be autoconvocado by a group of people, or responding to the call of a political force or another type of organization , generally against a government or certain governmental decisions or policies, and more Rarely for a cause. Translated from Wikipedia from Spanish to English.