As others have stated, there are plenty of grizzlies in there. Did a 26 mile through hike in there in late August of 2011 and we ran into two different grizzlies in three days. One of them was across a lake and didn't bother us. The other one was about 100 yards above the trail and it false charged us; it definitely got my blood pumping!! Met a couple of guys on the trail with llamas that were heading out early due to a grizzly encounter.
Also, as previously stated it was in late August and it snowed on us two out of the three days so be prepared for inclement weather.
Two weeks later I was bow hunting solo in a drainage over from where we hiked out of and ran into three different piles of grizzly scat. When I saw the first one it wasn't a big deal as I knew they were in the area. Then ran into the second pile and then the third. Since I was sneaking around the woods in camo, scent free (as can be) and making cow elk noises with a visibility of about 35 yards due to the thickness of the timber, I decided to back out. When I was walking out someone had written in the sand on the trail by the wilderness sign, "Danger grizzly bear in area".