welcome to the site, yvonne
im not sure about china, but in korea, if a ethnic korean comes back to korea to teach english, they find and teach the same jobs as folks with the "foreigner" look. sometimes its more difficult for them but usually not. my one friend who was adopted from korea has a great job at a university.
i don't know much about teaching in china but you might ask some more people about your situation. i bet it's not as bad as your friends made it sound. then again it may be.
post a question in the forums and see what kind of response you get. i know there are a lot of people on eslHQ that work in china so they may be able to help you a little more.
welcome to the site and good luck with your new adventure!
eric