According to the official US Raiderz Forum post there will be 4 US servers:
US West: Crawler and Fleetfoot
US East: Chimera and Diago
You can play on any server you choose. All characters and names from Alpha, CBT, and the stress test are wiped and will not exist when Open Beta begins. Feel free to pick a server you want to play on with friends or somewhere regionally close to you.