Getting most coverage/download speed out of Three Airport Extremes & One Express

Question

Aloha Apple Genius's please....HELP:-)
I have been having the following coverage/download speed issues with my new network installed in a couple of our buildings.
     A) Mac gets 0.5 to 1.5Mbps download and 4.0-5.0Mbps upload and it connects to stongest signal given off by 9WBB Building #2...But Slower Speed
Sitting on the Porch or in Building #2
Network Normal:
Strong Signal
Slower speed
     B) If I TURN OFF 9WBB Mac gets 15-22Mbps dowload and 20Mbps upload connects to weaker signal given off by 9WB Building #1....But Faster           Speeds.
Sitting on Porch or in Building #2
Network limited:
Weaker signal
Faster Speed
QUESTIONS:
How can I maximize the download speed or manually switch which Airport Exteme my Mac connects to with out having to power down 9WBB Building #2 all the time?
     2. Or can I tell mac to always pick SPEED over SIGNAL STRENGTH??
     3. How can I better monitor my network and speeds?
     4. Can I block users from using network individually?
I have a network set up with the following schematic:
Building and Physical Layout of Network below:

Answer 1

Anyways, I guess what I'm asking is if there are any settings I can use to simply allow my internet to be as fast and as consistent as possible, albeit a rather hopeful and juvenile request.
The Internet speed vs. the wireless network speed are two distinctly different things, with the wireless network speed, in almost all cases, being much faster. Of course, since most of us see "speed" as the overall time it takes to, let's say, open a web page or download a file from the Internet, it's easy for us to "combine" the two.
Unless you work with your ISP, there's not much you can do about your Internet speed, but there might be something you can do about your wireless speed.
Since you mentioned that you have detected about a dozen wireless signals, it is very possible that you may have some form of Wi-Fi interference in the immediate area that is preventing you from getting a good clean signal.
I suggest you perform a simple site survey, using utilities like the following to determine potential areas of interference, and then, try to either eliminate or significantly reduce them where possible:
For Macs:
o KisMAC
o MacStumbler
o iStumbler, or
o IPNetMonitorX
For PCs:
o NetStumbler
o WiFi Hopper
o WiFi Owl
o WiFi Manager