The site for the PaB wall inventory is Brickbuildr but they have not updated it in almost a year. If you call them at 1-216-378-2060, you can ask what they have or possibly ask them to update it. I have yet to find a LEGO store employee who will tell you everything that is on the wall, but if you call when no one is likely to be there (like when kids are still in school) you can ask about specific things that you might be looking for … like those earth tone bricks.
I personally do not like the pressure of standing in front of the wall during a long trip, trying to figure out what to get, knowing that a family who wants to get back on the road is standing there waiting for me to get my act together. Regardless, the smaller the parts, the more cost effective it is to get them by volume … of course only if you have a use for the parts.