The past few years, here's how it's worked.
- You pre-register for your convention badge, and, as part of that process, you are given a password to access the hotel reservation system. This means that you *can't* access the con's hotel block without pre-registering; it also means you can't reserve a hotel room via the convention's hotel block until the day pre-registration opens.
- Using that password, you then pick which hotel you want to be at, and what kind of room (1 bed or 2).
IME, the con rates are pretty good (the last two years, we've been at the Westin, which is a really nice hotel, for $120 a night). Fortunately, there's a ton of hotels within a few blocks of the convention center (some of them actually connected to the center), in various price ranges.
Also, count on pre-registration (a) not really going live until sometime after 12 noon PST, and (b) being slow as molasses on that day, once it does go live. Every year it's promised that it'll be better, every year it's not.