Talk to the guy outside the hotel on fountain rock. Be forewarned, this can be a very hard mission because there are loads of these guys. Take out the first three guys in the hotel and note the health kit in the room if you need it. Now head across the street and shoot the guys on the roofs. Keep moving, as they're equipped with sniper rifles.
After you've killed them, a new group will turn up in the hotel. Call a driver and use your car as extra defence. Drive around the hotel shooting all of them with some relative ease; it's a lot harder doing it on foot. Now head on up and use blind rage, as they will have taken defensive positions on the roof and can make Swiss cheese out you.
Now that you've taken them out on the roof, more will arrive via car. Get on the roof and use the mounted gun to make short work of them. However, note that the mounted gun doesn't cover the stairway up to the top floor, so always be aware of where they are so they don't sneak up behind you.