fortunately, most North American venomous snakes are very polite and smart enoug to know they have no business biting an animal to big to be eaten.
If you don't step on them or try to pick them up, the odds are very much in favor of them hissing at you once or twice and then leaving the area.
now, cottonmouths... they are a Rule unto Themselves.
I see that I have become infected by Darksheare's letter-thieves.
I use to catch Rattlers in the Mesa Verde National Park, so they could be relocated out of the public areas.
I've grown up a bit since then (by about 21 years)!! I can't believe I did that! I still like snakes, but I don't think I would be happy coming face to face with a poisonous one!