Im playing on Xbox 360. What i mean is , would i be able to sit at the Skyrim Add-on page and wait for the Dawnguard Download to pop up or would i have to do something different. And thanks not much experince with Add-ons since i normally download them the next morning but well its Skyrim .
No problem, you'll have to keep looking at the marketplace on the dashboard. I don't trust the DLC pages in games, the dashboard has never steered me wrong.
As far as the time of release goes, that's dependent upon what time zone you're in. I'm in the Central time zone, so if it's at midnight it'll probably be around 2AM for me, because that's when it's 12AM on the west coast. Sometimes that rule is followed, other times an add-on doesn't come out till later in the day.