I work in a factory that employs over 500 people... Not the only big plant around here either... so all of those people live in the general area. Yes, there is farm land, but how many people can farm in industrial scale without heavy equipment? I at least have horses and could probably rig things to use them for farming, well, 2 of them, the other one would climb a tree if you asked him to plow...I have about 50 within walking distance (comfortable walking distance. About 100 within 3 miles. Few thousand at about 11 miles).
As long as we stay at the 100 marker or less in my area, we would be fine if everyone could get along. Plenty of animals and farm knowledge to sustain. Only problem would be water.