Villa Riachuelo and Villa Real do not exist, but, i think i get what you are talking about, La Boca (a neighbourhood) is located south of the city, thats where Boca Juniors (a football (or soccer) club) is, the Riachuelo is a long nasty, super dirty and polluted narrow river.
From La Boca to Nunez the approximate distance is 15 or 20 kms.
it takes 20 minutes by car or 45 by bus. during rush hour, it can take you two times that.
Bue info in english