The following notes are not walkthroughs. They are tips for Xbox users who are having trouble getting through a mission.
Escuela Of The Streets
Top off your health/armor and have plenty of ammo. This is not a time-limited mission, so take cover and take your time.
The first trick is that to get into the building, you have to go to the roof of the next building and cross over. When you get to an open skylight, you will see a Bad Guy (BG) inside, but he won't notice you until you target him, so take him out quickly, then drop down inside and take care of business.
Your should not need a health boost if you are careful, but if you do, visit the coke machine.
The second trick is that when you reach the other end of the building, you can't get the door open, so you'll have to blast the lock.
This is a time-sensitive mission.
When the action starts at a garage, some guys will stay put and others will take off in a car.
Some walkthroughs say that you can go after the car and come back for the stragglers, but if it takes too long to get the car, you will get a notice that a BG at the garage escaped and you failed.
This can actually be a very easy mission.
When you get to the garage, you will be approaching it from its front left corner. Stay to the left of the street you are on. (Back up if you didn't recognize it in time. The BGs are not going to notice you until you fire.)
There is a big square post at the front left. You can pull up with your front left wheel right next to that post so that when you get out, the BGs standing on the other side can't see you.
Pull your automatic weapon and move to the left of the post so that you can see the two BGs and take them out. As soon as you fire, the car will take off, leaving one BG on the other side of the next post. Run around it quickly and get him, then run back to your car.
The BGs' car will have gone down a street to your right, but you want to go down the street right where your car is aimed, in front of the garage. If you watch on the GPS, you will see a red dot indicating that the BGs are heading down a cross street that intersects the street you are on.
You should be able to time it so that you broadside their car, smash them into the wall, and shoot them right there. (The fastest and easiest way is to stay in the car.) If you don't kill them, you are in for a chase in which you are supposed to try to bump and shoot their car, but they will probably end up on a cul-de-sac where they will bail out. You bail out too and you should have no trouble tracking them down.
But if you fire at them from your car during the chase, you will attract the police and when you bail out, the cops will be all over you, so it is better just to quietly follow them.
The Puerto Rican Connection
Following the train is pretty straightforward until you get near the end when the street you are on ends at a cross street and you have to go left or right. It looks like you need to go left, but if you do, you'll probably end up in an alley and have to turn around.
If you go right, it is easy to catch back up the train again. When you turn down a brick road, the train will stop near some entrances to the subway. If you stop there and go up those stairs to confront the targets, they will go down the stairs past where you stopped and one will escape in a waiting car.
So instead of stopping at the first set of stairs, cross the road and stop at the second set. The targets will come down the ones on the left so get set up about 20 feet away, target the door with your automatic weapon, and wait for the first guy to reach the door. At worst, you may have to go up the stairs to get the last guy. Before the first guy comes out, look around for a cop on foot. If you see one, you WILL have to go up the stairs to get the targets.