El Beso has beginners classes several nights a week and they are good with beginners. If you want private lessons I took from a delightful young woman in BsAs. She speaks good English and is wonderful.
Her e-mail is [email protected]ela. you could tell her Jack referred you.
DNI is a ghetto for expats where they teach the kind of Tango you can learn abroad and you can only dance at practicas.
Also avoid La Viruta, Villa Malcolm, La Ideal.
I suggest you take classes at El Beso, mo/we/fri/sun at 8 pm. They teach what you need to know and no bullshit at all. They also teach you how to dance on a crewded dance floor.