We think it's because of the Chilean elections, which were today. I suppose someone won, but I haven't been paying enough attention to the situation to know much about anything, except that there have been campaign posters everywhere for the entire time we've been here. Boy, it sure is a lot of honking!
Update from Sam: it's now been almost an hour and the honking is still happening! I almost can't believe this is all for the election, but we don't have a great way to figure out what is going on. Maybe we'll try watching TV in Spanish to watch the news.