I would not buy the puppy from the pet store.
For a couple reasons. If I wanted a dog I would either adopt from a shelter, or if I wanted to get a puppy of a particular breed, than I just don't see any advantage of getting a puppy at a pet store over a breeder. On the other hand I see tons of reasons to go with a breeder over a pet store.
That said, I don't think it's definately wrong for puppies to be in pet stores. I agree that in all cases that I have seen personally, it looks pretty grim, and I won't support those stores. I just can't see making a blanket statement that I won't support any pet store that sells puppies (or supporting any sort of legislation against allowing them too) because I don't think it's impossible to keep them humanely in a pet store.
But the question makes an important point, which is more important than my opinion on the matter. We have more power with our dollars than we do with our opinions. And if we think the individual store is wrong, we should feel obligated not to buy even a cricket from them. The chain stores especially, actually will use the ethics we want them too- Provided we are able to communicate our wishes to them. That's why I do use those "how are we doing?" 800 numbers that are plastered all over the place in the stores too.
And Mike, I think we have as much power to stop the rattlesnake roundup as you have to stop foxhunting in the UK. I'm not assuming you want to- I'm just trying to put that into perspective. I for one though, would not spend a cent at one, nor will I likely ever find myself in Sweetwater TX. If I try to send an email to any reps in TX, it's not likely for them to feel any pressure from the words of a Californian (lol, angry words from Californians in much of this country lets politicians know they are on track!) who can't vote against them anyway. And as for swaying the opinions of Texans who can, well all the Texans I know are here, and I'd probably be preaching to the choir on this issue!