It is not common for elves and humans to mingle, and mainly happens with traveling merchants and adventuring parties unafraid to break down barriers. Half-elves almost always end up picking sides, but pretending a strong understanding of the other side of the fence.
Have to work hard building community because each half seems to think of them as the worst of both parts. Prejudiced folk tend to put them down and they sometimes find themselves wandering rather than settling into a community. They may practice the worship of the Elven Gods or the the old ways, or new ways of the Humans.