You will have no problem with english in Buenos Aires, there a many people that speak english well.
When I come to think about it the Buenos Aires Herald news paper is older than many Australian news papers.
In BA I will look into for accommodation in La Recoleta, Barrio Norte or Palermo. Any of those suburbs are very good.
DO NOT LEAVE THE BIKE UNATTENDED
Rosario is a big city and for sure you will be ok there.
If I can help you in any way let me know by sending me a pm
Cheers
Arthur

