After the fight with Lugo and Adams, you will be left off in a hotel lobby. Search the left side of the starting room to find an ammo box, and then proceed into the next room and up the stairs. When you reach the top, a cutscene will initiate. You will find yourself on an overhang overlooking the area below. Adams will kill the lookout for you, and the three of you will take cover and look over the ridge to the enemies below. There will be tons of enemies below. A conveniently located white phosphorus launcher will allow you to empty out the crowd below, much to the chagrin of Lugo, who will tell you that you shouldn't use the launcher and should instead try to fight the enemies on your own terms instead of stooping to their tactics. Unfortunately, the game won't really let you do this. If you try to fight the enemies using your guns instead of the white phosphorus, they will spawn infinitely until you are dead or out of ammo.
So using the white phosphorus launcher really is the most convenient way to get through this fight. When you launch it, you will enter into a black and white, AC-130-styled view looking down onto the battlefield below. Your squad will light up targets for you in red, at which point you should hit the right trigger to fire out some white phosphorus. You will have reduced the battlefield below to ash in no time flat. Just be sure to take out the targets when Adams calls them out, especially the vehicles.
After using the white phosphorus, you will be returned to your regular viewpoint. Head to the left side of the balcony and use the ropes to rappel down to the lower level. You will now have to walk through the havok that your assault just wreaked. Move along the linear path and watch out for the fires that have sprung up all over the place. When you finally reach the end, a cutscene will initiate and you and your squad will jump down to a lower level. What you find there won't be any prettier than what you found up above, though. After a troubling cutscene, you and your squad will begrudgingly move ahead to the next checkpoint.
Leave the massacre via the open door ahead and take cover behind the Humvee to the right. Many enemies behind sandbags will stand between you and the checkpoint. Hit as many as you can from your position behind the Humvee before leaving cover and sprinting up to the low wall on the left. Have your teammates cover youi as you sprint from this piece of cover to the small column protruding from the ground. Refill your ammo at the crate and push forward up the hill. As you reach the top, watch out for two enemies coming out from the sandbags in the middle of the area. As you enter the building, look to the right-hand stairs to find two more enemies. Kill them quickly and take cover on the low wall overlooking the chamber below. From this position, you should be able to shoot down on the enemies and kill them all off without putting yourself in too much danger.
When the majority or all of the enemies below are dead, head down the stairs. More enemies will come into the area from the back left of the room. Refill your ammo from the corpses nearby and get ready for another round. The enemies will take up positions behind the right-hand desk and behind the circular barrier in the center of the room. Use Stun grenades to keep the enemies in check, and hit them when they can't see to finish them off. If you are having trouble hitting a target, use your squad commands to order an ally to finish the enemies off. There won't be any special enemy types in this group, so you don't have to worry about getting too fancy with the tactics. After the battle, sweep the area for guns and ammo.
Head up the stairs marked by the waypoint at the back right of the room and proceed through the opened double doors ahead. When you reach the next set of double doors, press either the B or the O button to kick them in and proceed ahead to the next level.