Courtesy of CheatCodes.Fartoo.com
After level 2 there are territories you can take over. Once you have done about three of them you will get the grapple hook.
When you get your grapple hook fire it at a passing or attacking helicopter. Then, just reel your self in.
After you kill the man on the boat and finish the mission, you will get the agency jeep.
Attack Village With The Guerrillas
Use the following trick when you are taking over a village with the guerrillas. Ignore most of the enemies and charge towards the roadblock the government has up. Destroy it using grenades, a rocket launcher or timed explosives. Do this to each one, and the "Capture enemy flag" objective will soon appear.. Rush to it and press A to conquer that area. For other villages without roadblocks, such as the towns when a police car with a turret on the back appears, go in it. One of your teammates will also enter. Drive down street and your partner will gun down everyone. Then, capture the flag when instructed. Do not open fire on anyone on your team or they will kill you.