As previously mentioned, try switching to 5GHz if you can. It won't go through walls, which means that you need to locate the AP carefully to make sure you have coverage where you need it.
Agreed. The 5Ghz spectrum always seems so open and free. Not to mention that 802.11a allows for dozens of *discrete* (read: non-overlapping) channels.
To help with the "not going thru walls well" problem of 802.11a, I've found that a simple reflector placed on every antenna of your WAP can boost your signal by 10 - 12 dB (in a single direction) -- This is enough to make it through walls of a condo. It also helps reduce noise coming into your WAP as well as pick up the signal from your devices better.
They're very simple and cheap to make, too. Instructions can be found at the Free Antennas website. The designs work great for all Wifi standards.
"Here's something to think about: How come you never see a headline like `Psychic Wins Lottery.'" -- Comedian Jay Leno