The first thing that you must do during "Armadillo's Commander" mission is the elimination of two snipers, placed in the highest towers in the base. You can do this alone or by using synchronized shot.
The easiest way to finish this mission is to use the left flank. There, you can find imprisoned rebels that can help Ghost Recon to complete the mission.
Before you go through the gate, make sure that there is no snipers in the tower. When you are in the base, on the left you can see a cell. Open it and the now free rebels will start to fight with Unidad soldiers.
Unidad's captain is pointed by the yellow marker. The soldiers are busy with fighting the rebels so you won't have problems with getting to the building where the man, that needs to be interrogated, is.
Interrogate the captain and the mission is successful. If the number of Unidad patrols is increased, use a helicopter to leave the base.