When the mission starts, quickly get in to the nearby Patriot parked in Phil's Place, then drive towards the targets. This mission introduces you to the Detonator Grenades, which is spawned near the entrance. There are four trucks to destroy: two in Little Haiti and two in Downtown.
There are many ways to get them. You could try out the Detonator Grenades or use any other weapons, like the Sniper Rifle. The weapons you have to collect are inside the box that has to be destroyed at the back of the truck. You have to pick up these weapons even if it meant replacing your current ones.
When you collected two guns, the Mexicans will send back-up using Faggio scooters driven by the enemy with Uzi submachine guns. The other two trucks will drive more aggressively. Killing these enemies will earn you a $100 bonus. They will endlessly come so you can't hang around.
The mission is complete after you have collected all the guns and destroyed the trucks.