Street food is popular throughout Asia. Changsha was no exception. There were bun sellers, dumpling sellers, tsong (rice steamed in banana leaf) sellers, as well as the rather more sketchy "fresh" fruit and raw meat vendors. There were also various markets where you could get everything in one place. Except for the aforementioned fruit/meat stands, don't be afraid of trying the street food. I trust the stuff that's cooked!
The Hunan province is known for spicy food. I suggest you try everything! And if you're lucky enough to be invited into someone's home for dinner, you're in for a real treat.