I play on the Khaz'goroth server. It is an Australian server, but the server is in the states, so you shouldn't have any latency problems. The only problem is is that the server time is Australian-based so you will probably be 8 hours off if you live in the East coast, which I do. But you can download an add-on that will allow you to put in the time where you live.
Also, most people in that server are from the states. Honestly, like 75% are from the East coast so you should not worry about a low population or anything.
