I know a couple of full service private guides that are exceptionally well connected and speak proper English. They are not inexpensive... but they are the only folks that I would dare recommend since its my reputation thats at stake.
While there are plenty of free and inexpensive guide options in Buenos Aires, Im afraid that none of those experiences can come close to what a truly professional and experienced guide can offer.
I have no horse in the private guide race, just that because of my business activity Ive come in contact with many and the huge majority just dont make the cut.