I agree. You are better holding up in a hidden room/space for at least 30 days, to let things thin out and quiet down.
Sadly, I think that if all of the city folk take to the road to wander into the countryside, it will become a monumental death march. World War II had many such instances, as the Germans invaded Russia, and then the Russians counterattacked the Germans.
Interestingly, I was born and raised in the suburbs, and the suburban mentality (mindset) would be to STAY AT HOME, and not to think that they would be better off by wandering off into the country side. Suburbanites like things to be neat, and orderly, and they view their homes and little patches of grass as their castles, and the road and the unknown as highly dangerous. If they gathered anywhere, it would be at the big local high schools, which would end up being like horrible refugee camps.
Urban folks seem to me to be more pragmatic, desperate, and willing to take risks. So, they may all start walking en masse, and taking and burning. Luckily, not one in a hundred of them has ever handled a firearm or tried to live outdoors for more than 2 days. The few of them that would be armed would only have handguns, not rifles or shotguns.
I think the huge initial clash woud be between the walking starving urbanites, and the stay at home (and well armed) suburbanites. Remember, 50% or more of all homes in the U.S. have a firearm in them, and the vast majority of homes are in the suburbs!
Mannyrock