I think it depends on your natural ability to gain or lose fat. If you're one of those leaner, lightning-quick metabolisms, you might be able to get away with no cardio during a bulking phase.
Also depends on your diet. If you're using a bulking period as an excuse to eat like a pig, then you're gonna need that cardio regardless. But if the diet's good, you might not need as much.
But if you're like me and you put on fat at the drop of a hat, cardio is essential, even during bulking. I'm doing a bulking phase right now and I still do three days of cardio, 20-30 minutes each. In three weeks I've added about 8 lbs.