I come from Weng 'an County, Guizhou Province. Can I buy social security in Guiyang?

Yes, social security has nothing to do with your account, so you don't have to buy social security at the place where your account is located, but if you are sure that you live in Guiyang and buy it, although you can transfer social security everywhere now, the base you buy in Guiyang is high, and it will become a county level when you return to Weng' an in the future, which is relatively uneconomical for you. Personally, I think it's better to decide where to live and buy it.