Qucik question:
Will there be an option to get turned into a vampire in order to side with the Vampires or should I become a Vampire before the DLC?

From what I have heard there will be an option. It can also be fun to already have a vampire so feel free to start one if you are into RP.

Im positive they will give you an option, Id wait.

I don't think you'd have to be a vampire until they VL you.

Ha no one is going to give you a concrete answer until the beta comes out, and by then you can answer your own question

I am from the future, listen carefully you may not be a vampire in the Dawnguard faction. OOHHH, BASK IN MY IMMORTAL GLORY.