I generally do not wash my fabric before using it. I did a coin quilt with Bali Pops on a white background (I guess I felt daring that day). The only issue I had was when I used steam to press one of the orange strips. It did weep a little bit. I of course freaked out thinking about the rest of the quilt but I soldiered on. When I completed and washed it (I always wash the way I think the receipient will wash it. In other words, not carefully) there was no weeping or bleeding even from reds and the little bit that weeped from the orange came out. Phew! Disaster averted!
I will say this, though. I have been hesitant to use batiks like that on an all white background without prewashing. Just because I got lucky one time does not mean I will again. I would not pre-wash any precuts, though. Too much aggravation with those small pieces.