Yeah, I've been to Changsha a few times... A lot of people don't speak Chinese there, they speak something called Changshahua, which sounds like retarded aliens screaming at eachother. This probably doesn't affect you much since you don't speak Chinese,
but don't expect to learn it there. (of course, a lot of people there also do speak Chinese, but I would say the majority don't speak it well, and you'll be hearing much more retarded alien screams).
For a capitol, I would say it is not a big city. There's no subway system, and the airport has about 6 gates. Not an international place. The most famous specialty food is rotten tofu. It doesn't taste bad, but you can't get within 5 meters of it without
wanting to vomit from the stench of the cooking. For some reason, people think it is a good idea to cook it on the streets where people are trying to breathe.
Also, I hope you like hot peppers in all your food. The food is good though anyway.
Oh yeah, you can buy an apartment there for like 30,000 USD. I guess if you rent a 1 bdrm place it will be 500~1500 RMB a month (80-200 USD), depending on where you live. I'm assuming you're getting sent there by a recruiter since no one who isn't from Hunan
would ever willingly choose to live in Changsha, so you are probably getting sent to a very remote area and I guess the rent should be closer to 500 RMB.