I've actually done a bunch of these exact audits over the past week or so (earlier today I did 2 120-ish lists with the same $20 bonus at a supermarket). I even ended up doing all 5 of the visits for the local drug store over a few days (bonus kept going up so I kept taking 2 at a time).
My experience/tips - bring the print out in with you, and fold it over a few times so you can 'palm' it easily if a worker walks by. I just write the prices next to the name instead of in the 'right' section. Most workers won't even notice if the isles are tall enough that they can't see over them, or if they do they don't care - I did a whole section of feminine products while someone was stocking down the isle and they didn't bother me at all. Other shoppers may look at you, but again, they don't care.
Once you get the hang of it, the lists don't take as long as they say - I was getting the 50 items lists done in about half an hour, and got both 120 lists done in an hour and a half today.
If you're really worries and can bring someone with you, do it - you can either ask them to ask employees to show them where something on the other side of the store is if they're hanging around the area, or just use 'goofing off with my friend/family member while shopping' as your excuse for being in there so long. Or if you want, grab a basket, throw in a few items taken from areas you're auditing as you go around, and then just walk back around putting them away before walking out when you're done. If an area is in plain site of the pharmacy or something, write the items on a scrap paper real quick and if anyone does ask, tell them that an elderly/injured family member asked you to find out how much X items tend to cost because they need some but can't shop themselves. I've done all of those.
Oh, and a tip - if any sections are too close to the pharmacy counter (diabetes supplies tend to be in that area), try to go after the pharmacy closes to do that section. They tend to close up before the store does, and then you don't have to deal with workers there giving you weird looks.
Good luck! Unless the folks working at your local stores are way more involved in their jobs than they are in my area, you should be fine.
[edit] Realized I'm a day late, but hopefully this'll still help you in case you decide to try any out in the future.
Edited 1 time(s). Last edit at 06/05/2012 02:09AM by wackogirl.