i went to eco marathon 2009 germany..
ceramic ball bearings even though they are awesome are hideously expensive and rare to find.. most probably you will have to import..
use normal bearings from skf or ntn.. they are good enough
focus more on keeping your wheels exactly aligned.. use the michelin tyres recommended by shell
from my experience i found alloy wheels for bikes to be heavier than spoke wheels but thats upto you..
if its your first time try to source as much material as you can locally.. it is much easier and cheaper to manage the project that way..
which university are you from ?
i was in nust pnec.. one of the first teams to participate in ecomarathon.