Yes jennyp, even if you don't belive in God, science agrees space/time didn't exist prior to the big bang.
I'd rather say they agree that there is no "before" the big-bang. But hey, Physicist is here. If you don't believe me just ask him.
"prior to" in this context has not meaning.
How would science know what did or did not exist prior to the big bang? I believe physicists would agree space and time are part of this universe and it is currently impossible to know if they existed prior to it. Maybe they did, maybe they didn't.