Weak Wireless Signal, Airport Network Anyway?

Hello,

I recently bought an Airport Express (latest model), solely for the purpose of streaming music from iTunes to my stereo.

The problem is, my signal keeps cutting out. So I will hear the music for 5 minutes, then it will cut out, then it will come back, then it will cut out again, etc. Very annoying.

Why is this happening? Certainly part of the reason is my sad internet situation. You see, my neighbor and I share a wireless system. The router and home signal is in his apartment; I just have his password. It's a reasonably fast, reasonably stable connection, but not perfect. There's no changing it in the foreseeable future, however.

When I bought the Airport Express, the Mac salesperson told me that my sad internet situation wouldn't be a problem -- in fact, she said, I could link my Mac and my Airport Express without depending on my neighbor's wireless system at all (with no internet at all). But I haven't been able to figure out how to do that. In the event, I set up my Airport Express with my neighbor's wireless password.

Can anyone tell me how to set the Airport Express up in the way that Mac salesperson advised -- that is, with a "direct" link to my MacBook, without depending on my neighbor's internet system? Or other solutions?

Thanks,
Josh