Wulf Ratbane
Adventurer
Old One said:[She wants to make in INT check (or other appropriate knowledge check) as to her best guess for a starting point in the valley floor]
If you wanted to be completely logical about it, you could start at the marsh and follow the river west. You don't really know how far west you'll have to search but the limits of your map (and Rawley's scribblings) seem reasonable.
On the other hand, heading down on the west side and tracking back towards the marsh keeps you out of the immediate danger of the marsh, but if you descend down at the wrong spot in the valley (that is, actually descend east of the temple) then you risk missing the temple entirely before you head towards the marsh.
Regardless, someone with the Track feat will be of great help, once down in the valley, in perhaps picking out old (or new?) trails that may give some clue of past (or present?) temple traffic.