I thought they were both in the nightshade family?

Eggplants are in the genus Solanum (Solanum melongena) and datura are in the genus Datura (Datura stramonium or D. metel, or one of the other species). They all belong to the family Solanaceae but I don't believe they will affect each other by cross breeding. They are probably close enough that you could graft one onto another (some people graft tomato stems onto potato plants and they are just as closely related as eggplants and datura) but I doubt the pollen from the datura would turn eggplants toxic. Also, since most people cook their eggplants before they eat them that should nuetralize any possible toxins - I would think.

I would remove the daturas from the area but for another reason - eggplants are famously bug/pest magnets and by clustering all your solanaeceous plants together I would think it would only concentrate all the flea beetles in the area, and the potato beetles... etc.

I don't have the technical knowledge that John has, but when I grew datura, they were often covered with the same horned fat caterpillars as tomato and eggplants. They are in the same family. It probably would be a good idea to separate plants that attract the same pests.

I hadn't even considered the pest factor! Its my first attempt at a veggie garden. Its a mess. Things I didn't know needed to be trellised aren't, things that I thought I had enough room for are meandering into the next row. But I am thrilled. First, that I at least have a sunny spot and second, that things are actually growing. Its a whole new adventure. Dirtrx