Tricky.
Eyeballing it, given the way Ponyville is drawn in the opening credits, plus how it is depicted in street scenes, you're probably looking at about 300-350 sentients with about 80 houses, at least when the series started. This is a viable population for a close-knit rural village.
The bit that throws me though is the schoolhouse. it's depicted as a one-room schoolhouse and the only one in Ponyville. But the number of children in the class does not match the number of children out-of-class. Heck the size of the class doesn't match the number of children shown during recess periods. If the class size better reflected the number of children seen in recess periods, the 300-350 village size would feel about right.
Now, by the time the series ended withthe Friendship Castle and School, the way Ponyville got drawn changed and we're probably dealing with over 150, maybe 200 houses worth of people.So approximately 1,000 sentients.
Whether it is a town, a village, a city, a hamlet, etc. all depends on weird rules that don't 100% apply to Equestrian populations, like the presence of a Church or a Cathedral. We never really touched howEquestrians dealwith religion in civic way in the show, so it's hard to work that out.
