There's lots of palm muting and sometimes ringing out just listen for the changes.
Also when Brett plays C and Am sometimes he drops his pinkie on the third fret of the B 
He does this in the outro and in between verses.
Like so:
       C5      A5
E ----0-0-----0-0--------- | 
B ----1-3-----1-3--------- | 
G ----0-0-----2-2--------- | 
D ----2-2-----2-2--------- | 
A ----3-3-----0-0--------- | 
E ----x-x------x-x-------- | 

Hope I could explain that well enough. Anyway it's a really fun song with awesome 
Hope you enjoy!

C5
Tired muscles, tired eyes
A5
Can't sleep through this Oaxacan night
E5
He's kept away from dreaming, haunted by thoughts of failing
C5
The family whom he shares a bed
A5
A tiny room even less bread
E5
He cries out to himself silently
            C5      A5                        E5
I am not a man                no I am not a man
           C5                         A5
I am not a man  I can't feed my children
                      E5
This is no life for them

C5 A5 E5

C5
So he's out of bed with the sunrise
A5
He kisses his wife and kids goodbye
E5
Then heads north to the border To work, become a provider
C5
But gathered at the country line
A5
Are protesters all holding signs
E5
He can't read but translates perfectly

             C5         A5                 E5
I am not a man              No I am not a man
               C5                  A5
No I am not a man I'm just a Mexican
E5
Illegal immigrant

D5
The politicians the pundits the public debate
A5        G5                   F5
But one question's lost in policy
A5                                              C5
"Is a man not a man if he's born outside a boundary?"
D5
Stumbling through the desert alone and afraid
A5        G5             F5
He almost dies from the heat
G5
But he thinks of his family and that keeps him going
F5
He won't stop for death least the laws of a country G
Arrested is no threat
                              F5
when you're already living unfree

Unfree!

C5
So he works the fields from 5 to 9
A5
Plus any job that he can find
E5
Saves up all his money, sends it to his family
C5
Before he falls asleep at night
A5
A thousand miles from his life
E5
He assuredly repeats

          C5       A5                     E5
I am a human                Yeah I am a human
              C5                 A5
Yeah I am a human a father a husband
             E5
A global citizen

C5 A5 E5

                      C5               A5      E5
Not a debatable statistic
                           C5          A5        E5
I'm not your problem economic
                           C5          A5
I'm not a threat to patriotic
            E5
That's idiotic
     C5
I A5 A...