This post has about run its course, but I'll chime in one last time -- I agree with MickinColo; I lived in Colo. Spgs. for 25 years before moving to AZ. Never saw or heard of anyone who saw a grizzly; the consensus is "We think there are grizzly in Colorado, but aren't sure where." Pretty much covers it. As stated earlier, the bear you're most likely to find are black bear; they still come into the outer parts of the 'Springs and raid people's garbage. The big ones run about 350-450lbs; plenty big enough to ruin your day, but still within the capabilities of an '06.
Regarding an elk hunt, unless you're in really good shape or have experience at high altitude, get ready for a wake-up. High-altitude exertion is a humbling experience for anyone who's not prepared for it. Blood level does increase as stated earlier, but it takes at least two weeks for your body to adapt. That's mostly from an inrease in red blood cell count, which accounts for the "extra pint" that's claimed.
Elk are generally found at the higher elevations (say, 9000+ feet, depending on snow depth), and even when I lived there, the only time packing out 150lbs. of quartered meat was "easy" was when I was running nine miles a day. That was before the ATV's were popular, but you don't always know where you'll get your shot. Get in shape if you aren't already, and you'll have a much more enjoyable and rewarding hunt.
Lastly, the '06 is plenty of gun for CO game. Get some 165 - 200gr Nosler Partitions, and you've got it covered. A friend of mine still hunts with his 7Mag, and 165gr does in a 700 - 850lb dressed-weight elk every year. Most of the shots I got were in heavy timber depending on where we were hunting. The NW part of the state has larger, rolling meadows, so a 250-300yd shot is possible, but usually not necessary if you're willing to stalk in closer.
Good luck!
