HI Rhi,
No, the season will be in the last three matchdays. See this fixture
http://www.afa.org.ar/?m=news&n=5277.
'Fecha 17' will be while you are there. Surely, the League will be very hot, hehehe.
River Plate will play away, very far, but you have Boca Juniors against Arsenal at 'Bombonera' or one of the greatest derbies in Argentina, Independiente v Racing. This one is a little dangerous to go really, but it's your decision.
Other option is if any team play decisive games (quarterfinals surely) of Copa Libertadores, the South American Champions League. Usually, that games are Wednesday or Thursday. River, Boca, San Lorenzo will play the tournament.
What you can do in BA?
To drink/eat:
Palermo Soho or Palermo Hollywood, two old neighborhoods whith very fashions bars & restaurants.
To visit:
Recoleta neighborhood (If you like architecture and don't care dead people, the Cemetery)
Caminito in La Boca neighborhood,
Palermo Park in the Libertador Avenue
San Telmo neighborhood (you can do it same day that Caminito. Sat & Sun there is a market with antiquities)
Puerto Madero (recycling docks in the Port with rest & bars).
Corrientes Avenue (lot of libraries, theatres & the Obelisco, a monument where we celebrate sports victories like 1986 World Cup
)
To shop:
Córdoba Avenue (there are five/six blocks with outlet shops)
Santa Fe Avenue
You have to eat steak till dead. And pasties, pasta & pizza. Any pizza restaurant in Corrientes Avenue will be memorable, mainly Banchero, El Palacio de la Pizza, Los Inmortales or Guerrin.
I recommend you eat any kind of pizza with fainá, triangles made with flour of chick-peas. Veeeery traditional.
This one is a small guide in english made by City of Buenos Aires's Tourist Office. There are some circuits:
http://www.bue.gov.ar/imagenes_guias/guia_bsas_ingles.pdfHope I help you!