Don't know the percentage of armed guards, although it's an interesting question.
Here's an interesting article on the SG Nat'l Forest: http://outside.away.com/magazine/0797/9707dark.html (which is definitely not Mt. SJ).
I know there are two pot farms near my place, one that was just busted in Glendale just off I-210 and one just over the ridge from me in the ANF off of Big Tujunga Canyon Road that's abandoned. Have not heard of any evidence of firearms in conjunction with either.
Have to say it gives me the willies when I go off trail some times. I read topos fairly well and sometimes can see that shooting up a drainage can get me where I want to go. The only problem with shooting up a drainage is what might be shooting at me! Dang, I think I need a joint to calm down...
