REI has a one-time $20 lifetime membership fee. You would get more than that back in dividend at the end of the year if you bought a bike much over $200. (dividend doesn't usually apply to Outlet purchases or certain sale items though) For bikes, the 20% off coupon is only valid for the Novara brand.

Since your commute is less than a couple miles, you can do that on just about any bike. That said, I would encourage you to go somewhere that you can check out the bikes and ride them since you don't have ton of experience yet. REI or Performance would be great places to check out, as well as any local bike shops.