In you opinion could this be done in two to four hours?
2 hours to complete the imagery, rip and print? No.
That sign looks to be about 30 feet long. That's big even for large format.
What's disturbing and quite telling, is the resources that are available, at literally a moment's notice, for the Islamofascists to capitalize on an incident and use the global media to spread the message.
this could have been done at the howard dean DNC printshop