How does pre-ordering an album work?

There is a new album or EP by Bad Meets Evil coming out on 6/14/2011 It's a rap group with Eminem and Royce Da 5'9" well I want to pre-order it from the iTunes Store but my family and I are leaving for vacation before it comes out and I can get it on my iPod. If I Pre-order it, will I still be able to download and get it on my iPod when I come home or will I have to buy it?