Multiple Connections: Wireless 802.11g and Verizon EVDO

I am in the Army right now and have limited internet access. In the barracks, I have my xv6700 as my modem (which I can not tether (for full EVDO) nor transfer at high rates of speed), which works for standard web browsing and simple, low bandwidth games. I can go around post where there are multiple 802.11g networks that have decent broadband connections. Unfortunately, I'm not the only one who knows of this. So the bandwidth is split between about 10 to 15 people. Is there anyway I can use both the wireless and EVDO connections at the same time?
I've tried connecting at the same time already. All that does is switch temperarly from the wireless to the EVDO network, then switches back.
I am currently running Windows XP, but am unfortunately having to upgrade to Vista due to lack of drivers for my laptop within the next 2 weeks. I've already posted a request for help for drivers.
Thank you in advance.