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.