I use Amazon a lot.  For me, they usually ship orders out the same day or the next, but I have an Amazon Prime account which is sort of "enhanced" so they do things faster.  For normal orders, I'd say expect them to ship your order out two days after you place it, and allow one to two weeks for delivery via USPS (free shipping, usually).  Other shipping methods, like UPS or especially FedEx, will deliver your package faster.

But I think if you order now you certainly have time.

(Alternatives would be to purchase your music digitally, via the iTunes Music Store, or Amazon has a rather large selection of MP3 albums as well, where you instantly download the music after purchase.)

Ebay is always an option as well. The only problem there is that you have to make sure you read everything. I have only had one item that didnt really work and they said it did. So if you use them just make sure to read everything. Other than that Ebay is great!!!

How fast is EBay at getting stuff shipped though?

People are usually really good at getting stuff out ASAP.

I've used Amazon before and do not have the enhanced thing or whatever that Mikey has and they get here pretty quickly. You should be able to get them before you leave. Also, your school should have some way to forward stuff to you. Anyhoo, if you're that worried about it and it's not a huge secret to keep from people at your house, just send it to your house.