Surefall Glade  

Basically it's like this, if you attack a bear in the cave, (or you're attacked by one); and a NPC ranger or druid within surefalls see's you, you're dead meat. The bears are KOS to anyone their level and under with the expection of fellow rangers or druids. So if you're low level, and neither of those; never wander into the cave under the waterfall, if you want to live... =) Also bear and wolf killers in Qeynos Hills be weary of Holly Windstalker who will do the same if she see's you. (The same goes for Treants in other zones)

As for the faction thing, you should be fine entereing Surefalls if you're a good PC, even if you've killed lots of bears. Only the faction loss bears (like in the Cave in Surefalls) will affect your standing with the Jaggedpine and Protectors (Druids and Ranger factiosn).

Be careful of helping the Corrupt Qeynos Guards as you'll get faction losses with Surefalls for helping them and the other way around for helping the SF NPCs.