Without a picture, we can't help with an ID. The talc suggestion is not a helpful one, I'm afraid. A great many of the insect pests that our plants have to deal with never even touch the soil.

Usually that kind of egg is a slug egg, but I have not seen them attached to undersides of leaves. Use less water, to a point of slightly drooping plants. Also avoid strong sun, as cilantro doesn't do well in strong sunlight

i have them, too! they are likewise ignoring my basil and leaving eggs and crap on the undersides of leaves. I squished as many as I could but without some sort of pesticide I may lose them.

"Also, does anyone have a good remedy for keeping bugs out of the soil."

Do you want to kill all the bugs in your soil? I wouldn't advise this. Many bugs are beneficial and applying a treatment to the soil to kill all the bugs may do more harm than good in the long run. If you are having a specific problem, like insect damage on your cilantro, then address that problem, but don't nuke 'em all.