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:
       C (x32010@1)    AmE (x02210@1)----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!

CTired (x32010@1)muscles, tired eyes
AmCan't (x02210@1)sleep through this Oaxacan night
EmHe's (022000@1)kept away from dreaming, haunted by thoughts of failing
CThe (x32010@1)family whom he shares a bed
AmA (x02210@1)tiny room even less bread
EmHe (022000@1)cries out to himself silently
            C (x32010@1)    Am (x02210@1)                      EmI (022000@1)am not aman (x02210@1)               no I am not aman (x02210@1)           C (x32010@1)                       AmI (x02210@1)am not a man  I can't feed my children
                      EmThis (022000@1)is no life for them

C Am Em

CSo (x32010@1)he's out of bed with the sunrise
AmHe (x02210@1)kisses his wife and kids goodbye
EmThen (022000@1)heads north to the border To work, become a provider
CBut (x32010@1)gathered at the country line
AmAre (x02210@1)protesters all holding signs
EmHe (022000@1)can't read but translates perfectly

             C (x32010@1)       Am (x02210@1)               EmI (022000@1)am not aman (x02210@1)             No I am not aman (x02210@1)               C (x32010@1)                AmNo (x02210@1)I am not a man I'm just a Mexican
EmIllegal (022000@1)immigrant

DmThe (xx0231@1)politicians the pundits the public debate
Am (x02210@1)      G (320003@1)                 FBut (133211@1)one question's lost in policy
Am (x02210@1)                                            C"Is (x32010@1)a man not a man if he's born outside a boundary?"
DmStumbling (xx0231@1)through the desert alone and afraid
Am (x02210@1)      G (320003@1)           FHe (133211@1)almost dies from the heat
GBut (320003@1)he thinks of his family and that keeps him going
FHe (133211@1)won't stop for death least the laws of a country G
Arrested is no threat
                              Fwhen (133211@1)you're already living unfree

Unfree!

CSo (x32010@1)he works the fields from 5 to 9
AmPlus (x02210@1)any job that he can find
EmSaves (022000@1)up all his money, sends it to his family
CBefore (x32010@1)he falls asleep at night
AmA (x02210@1)thousand miles from his life
EmHe (022000@1)assuredly repeats

          C (x32010@1)     Am (x02210@1)                   EmI (022000@1)am ahuman (x02210@1)               Yeah I am ahuman (x02210@1)              C (x32010@1)               AmYeah (x02210@1)I am a human a father a husband
             EmA (022000@1)global citizen

C Am Em

                      C (x32010@1)             Am (x02210@1)    EmNot (022000@1)a debatable statistic
                           C (x32010@1)        Am (x02210@1)      EmI'm (022000@1)not your problem economic
                           C (x32010@1)        AmI'm (x02210@1)not a threat to patriotic
            EmThat's (022000@1)idiotic
     CI (x32010@1)Am a...