Does a customer have a presumptive right to make an inspection, within reason, of the food handling area where he buys food, such as the kitchen of a restaurant of the bakery of a supermarket?
Seriously? I’d avoid eating somewhere that allowed people off the street to go traipsing through the kitchen.
It may vary by local jurisdiction, but I doubt it.
The average customer is not qualified to judge whether a given food-handling area is up to code, they are more likely to bring in contamination than to discover it, and a commercial kitchen is a very dangerous place for even people accustomed to working in that environment.
No. My (food handling) business is private property. Not only do you not have the right to poke around in my back room, I don’t even have to let you on the premises if I don’t want to. You can go buy your food somewhere else if that’s a problem.
I’m not saying that is or is not my rule, I’m just saying that you absolutely do not have the ‘right’ to inspect the food handling area. If there’s a problem call the local health department and make a complaint. They’ll follow through on it. I’ve had full blown inspections (at the wrong time of the year) for pretty stupid complaints. Seriously, one lady complained that some of our food smelled like some of our other food. We were inspected, got a clean bill of health and they went back and told her everything was fine.
Also, in many jurisdictions the reports are online and in all of them you can go down to the health department (or City Hall) and ask for them, they should be available for you to look at via the freedom of information act.
Where I live having an unauthorized non-employee go into the kitchen area would be a health code violation. Mostly because most random people off the street don’t have their hair covered, gloves on, there are some places that require special clothes or shoes, etc. It’s also not allowed because they could theoretically sue if they somehow became injured while in the kitchen area.
And yes, most places have either a letter grade or health department information posted with contact information for who you can speak to to obtain more details.
And, in many areas, businesses display their health certificates on the wall for anyone to see. In most cases, it’s not well marked or emphasized, but look around. You’ll probably find a piece of paper tacked up somewhere from a local or state department of heath certifying the business. Many of them say on them that the certificate must be on public display. So yeah, you can just walk into McDonalds and look around and find the little sheet of paper from the City saying that they aren’t known to be horrendous slobs.
There is a Mexican restaurant in Orange, CA that has two dining rooms with the kitchen in the middle. One day we were led through the kitchen from one dining room to the other. A coworker was disgusted – not because we were allowed to walk through the kitchen, but because she saw meat being chopped there. She eats meat, but she didn’t want to see it being prepared. 
I’d put a lot more credence in the actual reports then the certificate. You can look back at a few years worth of reports and, for example, they could say “Raw chicken dripping onto cooked hamburgers”, “Soups kept at 120 degrees, should be 155”, “No hot water at kitchen sink, owner said hot water tank needs to be fixed”, “No bleach for sanitizing work surfaces” etc etc etc, but then everything is fixed at the 30 day re-inspection and they maintain their certificate. If you see problems year after year after year, it means the place is probably dirty and they’re just cleaning it up for the inspector.