Spanish classes in Argentina? Well, I am not a Spanish teacher here in Mendoza, but have been teaching English for several years (here and in BA, at many of the schools that also have Spanish classes for foreigners), and I am familiar with many of the Spanish schools and teachers here, and have talked to a lot of foreign students who have studied Spanish over the years.
Yes, it is true that most Spanish teachers do not have qualifications or training to teach Spanish in Argentina. In fact, many do not have teaching qualifications at all. There are few places to get training as a Spanish language teacher in Argentina, and most that have teaching credentials have English or Spanish Literature credentials. The best teachers have DELE certification to examine from the Cervantes Institute of Spain, but do not believe schools that say they or all theirtechers are certified by Cervantes, as there is no such thing (they only certify a limited number of teachers to give exams).
Also, there is no such thing as a "certified" language institute in Argentina. There are advertising groups for "partner schools" that call themselves associations, but they are just a loose net of different schools that join together to give "recommendations" in different cities. For example, the " SEA - Asociación de Centros de Idiomas " which has many "member schools", has no real educational development function at all, it is just a way for "member schools" to advertise, and many of their schools are terrible (I know, because I have taught English at many of these schools, in BA and In Mendoza, at one time or another). Be carfeul. The best way to be sure is to get personal recommendations or references from former students. Some of these schools have some good Spanish teachers, but most are only mediocre, it is often a question of luck.
Chains like "COINED" are in fact franchises that pre-existing schools buy mainly for the advertising and obtaining students. There is no consistency between the schools, and I know personally that many of them are bad. For example, Green Fields took over the COINED franchise in Mendoza from Andino, getting that franchise name (along with others) changed nothing.
Also, be careful of websites from places like New York, Madrid and London who say they have "schools" in places like Mendoza or BA. They are nothing more than agents that charge large sums to Spanish schools in Argentina as a way of attracting students, which is the big battle here. If the sites (and probaly they are the majority of the sites that you get after a search) do not give the address and/or telephone number of the school (because they do not want you to contact them directly so they lose their big commission), do not deal with them. Be satisfied only after direct contact and after you feel confident in the school administrator or teacher.
There are some excellent Spanish teachers in small schools or who offer private lessons to small groups and individuals. For example, I have had excellent comments form foreign tourists and expats I have met in the cafes about Spanish instruction from:
http://www.cheeseandcrackers.ca/a/a.htm
Also, be careful about the accomodation arrangements of many of the institutes or other places, either they are overpriced or they are homestays wghere you are not really welcome. Again, personal recommendations from many students are always the best measue.
Yes, some of the larger schools are an option for fun activities, but be careful and do not believe everything you hear.
They can be very expensive. It is best not to be pressured into too many hours or paying for a long time. Pay only for the week, then you will not feel trapped and can explore other more suitablle options.
For comments from various Couchsurfers on studying Spanish in Mendoza, check out the thread from the CS Mendoza section:
http://www.couchsurfing.org/group_read.html?gid=4140&post=2940974
Enjoy your visit and studies here in Argentina, it is always a pleasure to run into people like you!
Buen viaje! :)