If a rooster is kept with the laying hens, then I would consider the eggs likely to be fertilized.
If you were planning to hatch chicks, you would check the eggs.in front of a bright light (called candling) after a few days of incubation, to see if you can see the beginning of the umbilicus. The shell does not get cracked.
You can't do this if the egg has been gathered for sale - room temperature or refrigeration stops the growth process.
Yolk color and flavor are better with healthy hens, but there are still variations depending on breed, feed, etc.
I live in the city, but I have an egg lady who sells her own eggs. I've visited her little farm, about 20 miles from where I live. She commutes to the city, so I arrange to pick up my eggs here. I found her because she advertised on craigslist.