[AngelicaDeAlquezar]

I may be very late about this, but "de pueblo" often has a pejorative meaning to express contempt and underline the "inferiority" of a small town when compared to a big city. The big city is supposed to handle much money, better educated leaders, more access to technology and development, while a small town is usually associated to being poor, underdeveloped, uneducated, etc.

So "ayuntamiento de pueblo" may well refer to the characteristic resource-lacking governmental institutions in a small town.