I beat it on delta the first run through, I didn't want to run into any english speaking north koreans
I took me two nights to finish the game, I was being stealthy for the most part and did all the side objectives... I'd say it took about 10 hours.. if I would have lowered the difficulty I could have probably knocked off an hour or two.
In the jungle I would avoid large firefights for the most part until I got to a good position that I could defend, when I came upon a village or a base I would go in stealthily or distract the enemy(with a big explosion or sniping some dude away from me), kill everyone and level everything.
You can only be stealthy up to a certain point in the game, after that it turns into just run and gun.