Heading for Parque Ichigualasto from San Juan, we this town on the map and our guidebook suggested that one should stop there if they were at all near, so we followed the suggestion. Vallecito is a crazy little town, of which the main purpose seems to be the celebration of Difunta Correa. You can read all about here here: http://en.wikipedia.org/wiki/Difunta_Correa
Super briefly, she is a woman who is credited with a miracle, saving her baby's life even while dying of thirst and starvation in the desert, and who many South American catholics consider a saint who helps the living. This is where she was buried, and a whole hill is covered with flags and plaques, miniature model homes, and much more. People ask her to help them get homes, cars, a husband or wife, or whatever else they want, and if it is granted, they bring something there to show their thanks. Everything has some variation of "Gracias Difunta Correa" on it.
We were here on a Sunday, and the place was packed. There was a line to the site, and all the restaurants and handicraft stalls surrounding the area were full of people. There was a celebratory atmosphere and it felt to me like the first time in Argentina that we've experienced culture that is markedly different from what I've experienced back home in the US.
After visiting the burial site we grabbed lunch at one of the restaurants and I had BBQ goat for the first time, and it was delicious.
As an aside, this explains all the roadside shrines in Argentina that are surrounded by full water bottles. People place the bottles there to take care of Difunta Correa's thirst.