Mike,

Unless you are traveling way before and after Thanksgiving, most other codes won't work. During the holiday period, Amtrak typically blacks out all codes. Additionally don't wait another moment to book your tickets, as most trains will sell out if they haven't already done so!

If you don't pick up the tickets until the day you leave, then you can get a full refund if you should get lucky and find a better deal somehow, some where.

But waiting could well see the trains you want selling out, or even increasing in price.