How will the public beta work?

Now that I've signed up for getting the public beta, (Actually, I did
over a month ago.) what happens from there? Will anyone be able to download
Vista or just the people who pre-registered? Will there be a limit on how
many people will get to download it? A deadline? The reason I ask this is
I will be going out of town on the weekend of the 26th-28th, and I'll be
returning on the 29th. This is my first time trying out a public beta OS.
When Windows XP was in beta, I didn't even know how to build computers or do
much more than the basics and said to myself when I looked at the ads,
"Windows XP Pre-installed, what is that? It must be another Windows. I
knew nothing about that. Hmm. Very interesting.".
(Now, less important history things for those of you who want to kill some
time.)
Back then, I was just starting to get comfortable with using a recovery
disc that comes with a computer and I got my first computer for Christmas of
2001, which I still have and use today, an eMachines T1090. I won't forget
it; the first computer we bought was in September of 1999. It was a Compaq
5304 with a Cyrix 250MHz processor, 64MB of RAM, a 56k modem, 4MB of video
RAM onboard, and a 4.3GB hard drive. (And a 32x CD ROM drive.) That
computer is also still running today believe it or not, with Windows XP. It
doesn't run any slower than Windows 98 did. (Which was pre-installed on
this computer, actually Windows 98SE to be exact.) Of course, it's got more
memory now. The 4GB hard drive is still also used as the only hard drive in
that computer. It only has the basics, but still has around half free
space. (Windows XP, anti-virus, and office software.) I've come a long
ways in six or seven years, from being seven years ago not even knowing how
to turn on a computer to building one only two years later. I knew within a
month after using a computer for the first time that I was going to get
hooked, and sure enough, I did. I did not realize, however, that I would go
this far.