Jut think of all the mice, pack rats voles etc those snakes git rid of. I have walked a lot of miles through the Montana sage, juniper hills, gumbo knobs and never had one strike at me. I have seen quite a few and they usually either stay where they are and go away from me. Prairie rattlers are usually pretty low on the venom scale and a 5' would be huge. The average rattle can strike 1/3 of its body length so if your just 18" away your good. Plus, they only go a few miles and hour and you can get way at mosey speed.
They do like hay stacks and feed storage areas because they are often high in rodents. Boots and watching where you put your hands has worked for me. But, never had one hit my boots that I know of. I have known a few people that got bit, but nobody had much trouble from the bits around here.