If you are thinking of going to lengus vivas, go on monday to register for inscription exam - and do it on monday, as it is very popular, especially with brazilian students and can be hard to get a place on the course. Its on av del libertador and Carlos Pellegrini - is you walk from retiro along libertador, there is a round building (20 or 30 floors) with claro sign on top, turn up there, and you will come to a building with yellow steps and red gate.
The school is good, the course is good, and cheap, but we had 2 teachers on the intensive basic course that i took, 2 hours each day, 4 days a week - 2 days each teacher, 1 teacher was very good, the other teacher wasnt, he was a nice guy, but always late, not organised etc.
I went to a Hilton in martinez to check them out/ sit in on a class, and the teacher was good, but the owner wanted to put me into a class with 2 others who had already been taking lessons for 2 months, and i had no idea what was going on. I got the feeling that they just wanted my money.