i will recommend "Gaint" . those bikes are really expensive 3000-8000 rmb. but its the best bike which u can get it in china. if you got a big wallet then go for that

you have several brands. the best ones, they´re not really Chinese... well, they are , but not... heheh
i mean, they´re from taiwan, like giant (a very good brand, yes).
most of the foreign brands that are sold here, are manufactured locally, so you can get some cheap models, with some reasonable quality.

i would advise you either Giant or Dahon (american, but made in China, by Yeah, if i remember well). Dahon has some pretty nice rides, and it´s world reference on foldable bikes. interesting in case you want to travel with it, or keep it in the apartment.
i got my foldable for 800 yuan, at Dahon.
If you buy from a well known company like these ones, you´ll have a better quality, so, no rust (almost 2 years on mine, and not rust yet), and better components, as well as assistance.
For really Chinese brands, i think Yeah is a reference, but mostly, the standards for the local market are really low, cause no one really cares.
you can count on some rust, broken or defective parts, as the QC is lower.
if you just want a simple occcasional ride, go to the next supermarket and buy the one you like the most.

Really wanna know.