You only have a Desert Eagle with one clip in it, so take down three of the guys rushing towards you and nick their weapons before heading down to the room on the bottom. Don't kill anybody else before you get that far, as after you've killed four people, reinforcements will arrive and you'll be made to look like a sieve. There is also a health pack in this room, so if you do take a lot of damage, you can heal yourself. Build up your rage meter and once it's full, charge out and take out the guys on the balcony behind you and anyone else you can see. After this you should be able to venture outside the room for brief spells and take out the odd person before ducking back in for cover. Don't get too close to the centre of the field though, as Sheffield has a bazooka. After you've killed a suitable amount of people, you'll get the message "kill Sheffield". Head on over to the side with the gate open to go up to the balcony. Head up and wipe out whoever is left and go into the room where Sheffield is and kill him (interesting to note you get different death scenes depending on what weapon you choose). Pick up the bazooka, aim it at the highlighted door to make a hole in it, and head down to it.
Once you go in far enough, you'll have a cut scene with Gomez. If you have blind rage, use it and head to the right and up the stairs and dive into the room to the left. If you don't have blind rage, fall back through the blown up door and take out anybody that comes towards you and build it up that way. The enemies are unlimited, so you won't get anywhere trying to take them all out before progressing. Once you've got to the room upstairs, build up your rage again by taking out the enemies coming through the door. Once done, keep going around the pathway to the end room, and take out the guys inside and anybody coming through the door. These aren't unlimited enemies here, and they seem to stop coming just before you get a full blind rage meter.
After they've stopped coming, edge down the steps and take out anybody you can, though it's probably best to retreat upstairs again, because they will start coming through the door and you'll be trapped from both sides. Build up your rage meter and use it to go down the stairs and chase Gomez into the small room at the side. Alternately, and something you can do if you get fed up with waiting in the room with the stairs, is use the blind rage in the room upstairs and then rush around the roof and down the stairs. However, you'll lose your blind rage before you reach the last room with Gomez, so you'll have to duck out the blown out door and build up your rage meter again, then rush into the small room at the back with Gomez. Either way, kill him in there and take out the remaining guards. After that, it's just you and Sosa. There is also a health kit in this room, for you to collect.
Finishing off Sosa
Oddly enough, Sosa is a pain to kill and will take loads of AK-47 clips in the chest and not even flinch. Keep low and duck behind the couches and fire at him whenever you have a chance. A couple well placed rounds to the head will be enough to finish him off. Also be warned; Blind Rage will be blocked for this final battle.
If you die at any point in the mission you'll end up right at the start, which is infuriating if you get killed by Sosa.