Like most of Argentina, New Year's has few public events, unlike the famed harbor fireworks in Valparaiso Chile.. In Argentina, it is a private time for going out to restaurants with family and friends, or staying home and feasting with family. After midnight, younger people go out partying. Many wineries, especially in Lujan area, have sumptuous New Year's dinners from sundown until ealry hours, often including music and dancing, but you have to make reservations and pay in advance. I have no suggestions, as I prefer to spend the time with a few friends and family here. Ask your hotel for a suggestions, but the parties will be expensive. Otherwise, be sure to eat earlier, as you may not be able to get into many of the restaurants later.
If you are spending New Year’s in the capital
Buenos Aires, you can go down to Puerto Madero, the old now-upsacle port, and see the fireworks that are put on by the city government shoot over the river. Alternatively, if you are eslewhere in the country, most people have their own fireworks and set them off in the garden or in the street.