If interference is that bad, try changing the channel on your access point. You stated in your first post you tried different access points with the same result, so I wouldnt be so quick to blame the quality of the AP. Try changing the channel and see if maybe a higher gain antenna will override this interference.
I live in NYC and I can clearly see 25 APs from my apartment with Netstumbler. Setting my AP to channel 1 makes my connection very unstable although channel 11 for me is rock solid.