Well as long as the eggs are clean without any significant poop on them, they are good to incubate. Some people do sanitize and wash every egg before incubation, but that is just completely unnecessary and can actually do damage to the egg. If there is poop on the eggs, feel free to wipe it off with a damp rag or paper towel though.
When an egg is laid, it is covered with a protective membrane enamel called the bloom, this protects the egg from dirt, pathogens and parasites from entering the egg. When the egg is washed, the bloom (protective coating) is destroyed and leaves the egg vulnerable to a number of things that could enter the egg and harm the developing embryo.
So you see...its best to leave the eggs unwashed unless you absolutely have to because of dirt or poop.