crowded wireless networks

Nowaday, wirelsss networks are setting up in everyhomes. Will these crowded networks interfere with each other?
Where I live, there are at least six networks with full signal strength around, two channel 1,two channel 6, one 8 and one 9. I setup my as channel 11 with WEP enable. Most of the time, I cannot connect to my network, sometime I do, I cannot get receiving signals (by pinging). I have to keep trying for half hours to two hours to finally get connected. Then connection drop from time to time.
Please advise. Thank