My bad... I was thinking of 802.11a, which hardly anyone knows about or uses.

Where IS my coffee?

Technically devices in the 2.8Ghz and 5Ghz spectrums are supposed to gracefully degrade in saturated environments. Phones actually do this very well but your standard wireless access point doesn't. The reason is that phones will frequency hop all on their own (if they are any good at least) where as the standard off the shelf WAP does not - the frequency must be set and typically comes set on channel 6. So what happens a lot of times is in one neighborhood everyone is using channel 6, if you change yours to say 1 or 11 or better yet download a program called netstumbler (google it) and actually see what channels are in use around you and which are not. You can then set your channel to the least congested. Ideally 1, 6 or 11 for 802.11b/g are the ones you want. They are the only channels that do not have overlap from eachother. The rest have some overlap (the "channel" indicates the "center" of the channel).

Having a 2.8 Ghz WAP and a phone on 5Ghz is great but both of mine are on 2.8Ghz and I have zero issues. I'm also using a fairly standard WAP54G from Linksys.