I agree with Tradtusker. I have a 25-year-old down bag from Beans that's been to Alaska a few times and out west practically every year. Never have I gotten it wet, and one trip in Alaska it rained 12 out of the 14-day hunt.
That bag is getting a little compressed after all these years so I recently picked up a Western Mountaineering bag. Very high quality, high loft down. New, they're over your price range, but might be able to find a used one.
I'd also recommend a 0 degree bag. I'd rather have a little extra than not enough. It can get mighty chilly when the thremals start running down the mountain at night. You can always open your bag if you're too warm. Of course, you can put clothes if you're not warm enough, but that's a hassle and rather uncomfortable.