Spike's made its disdain for Nintendo perfectly clear ("Wii GOTY: NSMBWii. Moving onto more imporant things: the candidates for the award for Best Lighting In A Sewer Scene (Nighttime)! are...*five minute montage*"), so it's no surprise that they're skipping the conference.
Regarding the timing, Eastern time is three hours ahead of Pacific, so G4's coverage will begin at 8:30. Presumably, with commentary rather than the actual conference.