To close the loop here, this is what we ended up doing: We met in Palermo at Serrano Square around 9 pm and had dinner and drinks at an outdoor restaurant (Baum). We also celebrated new years there. We went to a club *after* midnight (ended up going to Caix which was nice: had techno music and regatone in 2 separate areas. We booked Caix in advance on Passline). Clubs did not open till 1:30 AM even on NYE so it was a good call celebrating NYE at Serrano Square. Ubers and cabs were not easily available : the average wait on Ubers was like 15-20 minutes but we did manage to get them to and from the venue. I would recommend this above plan to anyone visiting BA for New Years, our group surely had a great NYE!