She won't join you right away, first you need to liberate the mine and the water station. Once you do that, come back and talk to her and she'll offer to join.

Skyrider crashed his Heli and wants his diamonds back. Crash ground is to be found on the Hick's farm (west of Cambria City), just south of the farm's buildings across the small river beneath some trees. Diamonds are located in the back of heli, just walk there to discover them. Bring diamonds back to skyrider to share them and get a special reward from him (You'll miss the latter if you trade all 4 diamonds for money on your own)

Eliminate the Hick's clan since they appear to be feeding on Arulco's citizens! Their Farm is located west of Cambria City. Go there and kill them all to please the Father. (Quest 'In the Sky with Diamonds' is also to be solved on this map)

Quest notes send you to Father Walker in Drassen City who sents you in turn to Ira. When she is ready to join you she also tells you where the rebel's hideout is: North of Estoni (and west of the Hick's farm west of Cambria). This area is free of enemies, so just go there and walk close to Miguel (the blue NPC at bottom of the shacks nestled to mountain side) and talk to him. That's all.

Miguel wants you to ally with local criminal mob since they are also interested in getting rid of the Queen and therefore probably willing to invest in your efforts. Thus Miguel sends you north to San Mona to make contact with the Kingpin. This quest becomes solved once you eliminate enemy forces in and around Kingpin's Mansion in the southeastern part of San Mona. But Kingpin is neither willing nor able to pay you - not before San Mona has been freed completely by you. So you have to fight on, conquer San Mona City completely!

Once San Mona is no longer controlled by the Queen's army, Kingpin sends you to his henchman, Iggy. You can find him in the big central bar in San Mona City. After talking to him you recieve Kingpin's promised reward (50.000 bucks) and access to the arms dealers (who refused to trade with you until now). Iggy is furthermore willing to join your ranks! Talk to him again if you want to add a well rounded low level fighter to your team for free.

Miguel wants you to bring him the diamonds that had been smuggled and hidden from the Queen's grasp by mine workers to aid the resistance. The corresponding quest item is "Oswald's Diamonds" and they are to be found on map "Water Pump" south of Drassen City: There is a large wooden shack beneath some trees north of the water pump. Search for them in the northern surroundings of the shack; by walking to and fro you will eventually discover them. Hand them over to Miguel and he is willing to join your ranks.
Remarks: Most probably you have discovered Oswald's Diamonds much earlier during your first visit to the water pump following Ira's quests. If so, bring them along and you can complete the quest immediately after receiving it by talking to Miguel again.
If you have sold the diamonds yet you can re-buy them anytime later to complete this quest.

Dimitri wants you to dry up San Mona's drug quagmire. Your first mission is hence to stop drug production on a farm east of San Mona City (follow the road heading east out of San Mona if you need more exploring to find it). Just bring down any opposition you meet there to solve this quest. (Tho the mission briefing might have implied, there is no need to bring along explosives in order to burn down the plantation or something like that; just kill all guards and you are done.)

To finally stop drug supply, Dimitri wants you to conquer Kingpin's boathouse. The boathouse's location is called "Hideout" on the strategic satellite map; It's east of the drug plantation, across the stream system, north of the University of Cambria. Just bring down any opposition you meet there to solve this quest. Report back to Dimitri and he is willing to fight for you.
(Tho the mission briefing might have implied, there is no need to bring along explosives in order to burn down the house or something like that; just kill all guards and you are done.)
Easteregg: take note of the map's name on the loading screen ...

Brenda needs new female gay porn! You can find one right in San Mona, in the brothel in the northwest (the building with the redish roofing tiles). Hand this magazine over to brenda and she will reward you with some toys for your heavy weapons (Automatic Rocket Rifle + ammo) and explosives (several C4 with timer) guy.

Note: In the mentioned brothel you can also find a diamond called "Skyrider's bag of diamonds". But it is not connected with the corresponding quest! Do not merge it with Skyrider's diamonds you have found at the Hick's farm. Best to do is sell it right away to avoid confusion (and get some thousands bucks for it).Fixed with v1.11; no diamond anymore.