The statues are all accessible from the caves. If you walk from the 'start' of the trek through the caves, you will eventually find a way to all of them by hugging the right side of the wall(s). The doors open (a la 'chicken level') from the wall when you get close to them after activating the previous statue.
I can't remember exactly how many statues there are, but by the time you reach the last one (the one with the chest), you will have made a bridge across the buttes (hehe...Indiana Jones flashbacks

).
The chest holds some pretty nice magic items (equivilent to a low-level Grescal/Star-Key drop) and is definitely worth getting at this stage of the SP game
S_S
EDIT: I don't remember the quest to clear the pass to Glitterdelve from Stonebridge...the only quests (3) I actually remember from my journal were the:
1) AXE (located in the tower basement, on the ridge, toward Stonebridge, near the Glitterdelve gates)...I had to go back and complete this particular quest, as well.
2) Deliver Gyorn's (sp?) MESSAGE (but that's not until we get through Glitterdelve).
3) A Sister's MESSAGE (or something like that...not until the town after Glitterdelve either).
I blew up the barrel and spoke to the Guard Captain on the other side, but my journal never showed a quest nor did it show me completing one after the conversation.