Sepia,
By all means, go early. You can eat on $10 a day (and I mean EAT as in stuff yourself!), and it's even cheaper in the country....more like $1.
Do you hike? If so, check here:
www.beijinghikers.com
Every Sunday you can count on a great hike. You'll definately learn the land a bit, meet a lot of interesting locals, and have a lot of fun.
Tianjin is HOT in the summer so bring your summer digs. I'm talking hot, dry, dusty, and miserable. Fun though. Like Beijing, it's a big government HQ, so the attitude is not as laid back as Shanghai, and the inner cities. Too many politicians. The food there is quite unique. A lot of seafood, and a creamed cabbage that is REALLY good. As you are probably reading up on, Chinese food is different depending on the province it's from, and such. From seafood, to spicy.
Do you scuba dive? I have a good friend who is PADI's only IDC guy in China, and he's in charge of bringing PADI into China. There's a sunken city up near where you will be that is a great dive. They built this dam and flooded the city, and it's now under 30 meters of water. Cars, books on the library shelves, and all. Fascinating dive.
Anyway, tell me more about when and where you'll be going, and I can put you in touch with some good people. I'm certain we'll meet up too. I'm looking forward to it.