Asura has a pretty strong San d'Orian heritage, I'd say a good 50% of the server or more are San d'Orian.
That being said, all of the starter cities on every server are going to be ghost towns. That's the downside of starting fresh in a game that's over a decade old, most players have progressed past the starting point and spend very little time there. Once you hit the central city of Jeuno, which tends to happen around Lv20-30, you'll start seeing a lot more people. Right now Jeuno & Adoulin are the two most populated areas and I think that'll generally ring true on any server.
____________________________Pergatory (Asura, Kupo LS) WHM99 ~ SMN99 ~ DRK99 "If you want to know me, look inside your heart." -Lao Tzu