Decided to buy, now when to buy?

After much research and oogling over reviews and youtube videos, I've decided I want to purchase a Macbook Pro 17" i5 with 8gb ram and 7200 rpm HD upgrades to replace my 2008 Macbook. I mainly want it for the screen space. Here's my concern: I go to school outside of the my home country (US) and I'll be returning for about 2.5 weeks in August. I'm pretty much set on getting it but I still wanted to check out in the store before buying. But I'm worried that if I order it when I get back, it won't ship in time. I've tried to see shipping times from other users and it ranges from a day to 3 weeks. So would I be fine if I waited or just let my impatience take over and put the order in??

Is there an Apple Store near you, where you could just walk out with it the same day?

Also some Best Buys carry Macs now.

I actually have tons of apple stores around me (Houston) but I don't think they customize macbooks. Correct me if I'm wrong?