The Buenos Aires Tourist Board office is, unfortunately, not open to visitors; however, you should have no difficulty finding little kiosks throughout the city where you can get free maps and information to help you navigate.

There is also a hotline for tourism information: 11/4313-0187.

The Buenos Aires Tourist Bureau has a very comprehensive and informative web page where you can find all sorts of information

http://www.bue.gov.ar/home/index

http://www.bue.gov.ar/home/index?&lan...

And as for actual tourist offices that offer maps and pamphlets and people to ask questions to here is a list (taken from the Tourist Bureau web pages.) I personally have used the one in San Telmo - so can vouch that it is open to the public.

 7 centros de información turística    
  
Aeroparque Internacional Ministro Pistarini, Espigón Internacional 
Address: Ezeiza 
Neighborhood: Pcia. de Buenos Aires 
Hours: lunes a viernes de 10 a 17.  
    
Aeroparque Jorge Newbery 
Address: Hall central de Aerolíneas Argentinas 
Neighborhood: Palermo 
 (54 11) 4771 0104 
Hours: lunes a domingos de 10 a 17.  
  
    
Florida 
Address: Florida 100 
Neighborhood: San Nicolás 
 (54 11) 4313 0187 
Hours: lunes a viernes de 9 a 18; sábados de 10 a 16. 
 
  
Puerto Madero 
Address: Alicia Moreau De Justo 200 Dique 4 
Neighborhood: Puerto Madero 
 (54 11) 4313 0187 
Hours: lunes a domingos de 10 a 18. En este centro también se ofrece información de la ciudad de Montevideo, Uruguay.  
  
    
Recoleta 
Address: Quintana 596 
Neighborhood: Recoleta 
 (54 11) 4313 0187 
Hours: lunes a domingos de 10 a 18 hs.  
    
Retiro 
Address: Av. Antártida Argentina (Terminal de ómnibus Local 83) 
Neighborhood: Retiro 
 ( 54 11) 4311 0528 
Hours: lunes a sábados de 7.30 a 13.  
  
 
San Telmo 
Address: Defensa 1250 
Neighborhood: San Telmo 
 (54 11) 4313 0187 
Hours: sábados y domingos de 10 a 18