Possibly. It might be easier to do inside SFDC.
But if you were to try this in Marketo, you could use Wait Steps and Lead Is Created Between X Hours.
If Lead Is Created, then Wait 1 minute ends M-F at 8am (although this wouldn't quite work).
So you need a way to know the time of creation which I see isn't super easy to extract. I'd do this in SFDC.