I have to say, I really like Linksys, and own several.
I get great signal outside even into my neighbors house and I can pick up his linksys as well
As others have said, construction and other interference are most likely.
I did a site survey of wifi in my area and everyone was on ch 6. About 6 or 7 different ones. I went to ch 1.
I also use wrt54g, however I have mine hacked with 3rd party firmware. You can even turn up the power although I have no need for that. The hack also always turning a linksys router into a repeater if needed and this is cheaper then most repeaters.
The firmware also allows for more SSID's to be broadcast, even on different channels and with separate encryption.
http://dd-wrt.com/site/index
Also make sure you encrypt. I like to use mac filters for wifi.