I think if it's dry
enough to attract mice you could pick it. I'd shuck it and spread it out somewhere inside, maybe with a fan.
This is my first year growing popcorn, but I've grown lots a sweetcorn for many years and some field corn.
What kind did you plant? I'm growing Smoke Signal. I think about 50 plants. I thought, it was doing good. I'm gong out to check for mice now