Use the following trick when you are taking over a village with the guerrillas.
Ignore most of the enemies and charge towards the roadblock the government has 
up. Destroy it using grenades, a rocket launcher, or timed explosives. Do this 
to each one, and the "Capture enemy flag" objective will soon appear. Run to it
and press A to conquer that area. For other villages without roadblocks, such 
as the towns when a police car with a turret on the back appears, go in it. One
of your teammates will also enter. Drive down street and your partner will kill
everyone. Then, capture the flag when instructed. Do not open fire on anyone on
your team or they will kill you.