Why would training your abs have any effect on bulking? It's true that abs are only visible at lower body fats but its not true that doing some ab work is going to get in the way of gaining muscle.
stronger core = bigger lifts = more muscle
In my opinion cardio should never be completely abandoned as it does so much for your health aside from weight loss. Don't over due it and start running marathons. You can always compensate for burned calories by eating more.