Honestly, there are only 3 802.11b/g channels, 1, 6 and 11, so there are not many to choose from.
To verify what access points are in what area, download Aruba Utilities from the Android Store for an Android phone and see what access points you can see from your phone: https://play.google.com/store/apps/details?id=com.arubanetworks.arubautilities&hl=en
Seeing more than one access point on the same channel is not bad, as it is the level of traffic they are handling that would determine how bad the cochannel interference affects your clients.
I would make sure:
- You are using 20 mhz channels
- you have drop broadcast and unknown multicast enabled on all of your Virtual APs...Broadcasts are the enemy of wireless and cause disconnects
After you have done those two things, you can then look at how many access points are on what channels.