I would think when Captain America 2 comes out that Steve will be a little more familiar with today's world. Don't you think?
He was using a bluetooth wireless headset with no issues during the New York battle
Sidenote: Re-watching The Avengers I noticed that the team doesn't stray too far from "Grand Central" station.
The production crew just makes one small stretch of highway. The rest is all CGI
-Where Hulk punches the chitauri creature
-Where Hulk puts down Stark.
It's a neat little film making technique.
And considering most all of the street shots were filmed in downtown Albuquerque
.. Loved seeing familiar store fronts and buildings mixed in with the CGI New York...