Actually, with all the fun I had from last October through May with fluid build up and other assorted issues due to the heart surgery, I sure learned a lot about the body and fluids. Basically, a healthy body will self regulate fluids, so drinking a lot of water in advance of going out west is only going to make you have to pee a ton here in the flatlands.
The best thing you can do in advance of going out west is cardio exercise. Hit the treadmill, elliptical, stairmaster, what ever, but get that heart rate up and keep it up for at least 30 minutes a day. This should be started months before going out west, not weeks.
Once out there, then drink tons of fluids. You really cannot over do it. Somewhere on the order of 5-6 liters a day is a good starting point, but more can be needed by some. Drink mainly water, but sports drinks are good too as they replenish your electrolytes. Another one that is good, but can be hard to follow while on vacation is to avoid alcohol and caffeine as both will dehydrate you.
Carter is right on with the pee color. Clear is good, the darker the yellow, the worse off you are.
Folks might want to
read up on AMS. Not trying to scare anyone off, but it's all good knowledge to have on hand so that you can differentiate between a mild case of AMS and severe case.
-John