The weights that you use for a national-level analysis would apply for any sub-population, whether defined geographically (e.g. a region) or by some other cross-cutting variable (e.g. urban areas or the highest wealth quintile). Means, for example, that are weighted by v005, will be unbiased estimates of population means or sub-population means, however defined.

When you get down to a small subpopulation, such as the urban population of a single district, with very few clusters (maybe only one), the estimates will obviously deteriorate in quality. The standard errors will go way up because the sample size is small. However, the point estimates will still be unbiased.