I stayed at the modest and conveniently located NH City & Tower Hotel, walking distance from San Telmo, Florida Street, Casa Rosada, Puerto Moderno and nearby downtown.
The room is small, but adequate, dressed simply, is comfortable and has hardwood floors. It oddly feels quite homey. As with any city, I'd take a bit of precaution coming and going at night. The area around the hotel thins out.
I've stayed at this hotel twice and will gladly, again.