In my experience with Petco, at least the one here. If they start to go down hill and you stay on them about it they will keep things at the very least clean. They won't stop overcrowding but at the very least things need to be clean, water, tanks and food.
Be careful though, I have known people who worked at petcos that were reptile keepers and they were caught giving out the correct info versus petcos policy and caresheets and were fired pretty much on the spot. They have their policies and won't let you go against them.
So when I go in there I have shut down employees giving out wrong info to customers and I have given the correct info. Including websites, and forums. I have referred a few people here in the last week or so.
Just don't let them get off track.
Kristy