Rattlesnakes can be almost anywhere in Oregon. I used to think they were never found in the Willamette Valley. Then I found out that there are rattlers around Spencer's Butte in Eugene. At any rate, they are most prevalent in the dryer regions of Oregon--Southern, Central, and Eastern Oregon.
Snakes will sense your presence through your body heat and movement. They can feel the vibration of your step. They may rattle their tail or they may not. They don't like to be around you any more than most of you like to be around them so they will crawl away if given the chance. Most of the time when you are out hiking this is the best thing to do--just let them go. When they are actually in your camp you most likely will have to kill them.
Most rattlesnake bites occur when the snake is startled and hasn't had an opportunity to run away. This can happen when you are walking in tall grass or weeds. It can happen when you pick up a piece of wood from the ground. It can happen when you reach up to grab a rock ledge and the snake is there warming himself. So be careful in tall grass, around logs, around wood piles, and around rocks. Also, rattlesnakes can swim. Don't pick up that "stick" floating in the water. Never reach into a dark hole. It is a good idea to wear ankle high boots when hiking. Never walk barefoot or in sandels.
As I explained on the Oregon Wildlife page, my encounter with a rattler was at the edge of a river. The snake's head was just inches from the water and it was lying on wet sand. It is likely that I was saved because the snake was too cold to move fast. That's my theory anyway.
If you kill a rattler be aware that even though it is dead, the venom is still active. A dead snake or snake head can still bite through a reflex action. Remove the head with a shovel and bury it. Do not handle the head with your hands. Yellow jackets like to feed on dead snake. If they injest the venom and later sting someone, the venom from both the yellow jacket and the rattler is injected into that person. I have just found out that this is an "old wives tale" about the yellow jackets. Oh well, I still don't like leaving the snakes head laying around.
In the winter time rattle snakes stay in dens together. These can be caves, cellars, hollow logs, hollow tree stumps. They leave the den and become active in spring, summer, and fall.
A rattlesnake bite is a serious thing and must have medical attention. Few people die from the bite but it can make a person very ill. Children especially need quick medical attention.
If you or one of your party is bitten:
Often the nearest help is a Forest Service Station or Guard House. Know where these are located before you enter an area. You cannot count on a mobile phone working in mountainous areas. Educate your children about rattlesnakes.
Don't camp or hike alone.