I've done nearly 2000 miles offroad in Baja. I don't ever NEED 4wd (except for that one road to San Sebastian...) smile Mostly I engage 4WD when I'm flying washboard at 50-60mph and want that extra amount of control. Yes, I know flying is bad, but when you have 85 miles of trail to cover and the washboard is rattling your eyes out, you start to succomb to the magic of flying washboard.

Sand is your enemy in 2WD, but other than that, a 2wd should be fine. Most mexicans drive 2WDs and they go everywhere.