Hi Bobber, I lived in China for several years and was engaged to a Chinese girl when roughly the same age as you are now. If I may offer any advice for your trip to China, it is that, as strange as it may sound, meeting this girl should not be the most important part of the trip. The most important part of your trip should be getting to know her parents as much as possible and telling them of your hopes for the relationship.
Why do I say that? Well, there has arguably never been any two consecutive generations that have had such profoundly different life experiences as your girlfriend's generation and that of her parents. Should you not have an excellent idea of the many reasons why I say that then you really need to in order to understand your fiancee's culture. Anyway, these two generations have been shaped by profoundly different cultures, and think, feel, behave and dream very differently. However, nothing in China is as important as family. These two generations are inextricably bound together not only by tradition, and not only by the duty to provide for the parents in old age, but by the way the older generation, whose life chances were stunted by national turmoil, have poured so much of their hopes, dreams and ambitions into the raising of their one child - the only child they may have been painfully restricted to. They have made enormous sacrifices for their children, and don't the children know it... Their children feel enormous obligations to them, and many Chinese 20-somethings desperately want to make their parents proud of them and that all those sacrifices were worthwhile. However, these 20-somethings, as I said, have profoundly different cultures, experiences and values, which causes a big problem for them.
In my experience, the response many of these young adults have is to effectively lead a double life: one for familial consumption, one for outside the family. In many cases this causes no problem; the young person's interests or opportunities change and not having told the parents has saved unnecessary conflict. However, when the two worlds collide the fallout can be spectacular. Seemingly, very often the young adult tries to present something as a fait accompli in the hopes that, since nothing can now be done about it, their parents can learn to accept it. However, that strategy is not always successful. My own engagement lasted about as long as a mayfly, as the news of this was apparently the first her parents had heard of our relationship, and her father - her well-connected, charming, cultured father whose home was decorated with souvenirs from all his many business trips to Europe - exploded with rage at the prospect of his daughter marrying a "white man" and maybe moving to Britain. Her mother told her she was betraying them. She crumbled. (Your girlfriend has assured you that her parents would be fine about her moving to America? Well, substitute Britain for America and that's exactly what mine told me!)
Later, my best friend's relationship with his girlfriend, who he had cohabited with for two years, collapsed, and he travelled to her hometown in a last-ditch attempt to patch things up. Her village, particularly her parents, was scandalised by the news of her relationship with a foreigner. I have friends who are successfully married to Chinese women (and who all live in China) but there are other, similar, tales I could tell.
Even if her parents accept the idea of your marriage, there are many other potentially huge obstacles. Please don't go into the relationship thinking that in their old age her parents will certainly be happy with a monthly cheque from America and frequent communication. In China normally both parents work all day, and taking care of the youngsters is predominantly done by the grandparents. Once Chinese people have retired, their dominant function in life is usually to raise their own grandchildren. Very often, they will expect to live with their married child in order to do this. By taking your fiancee to America you may be threatening to destroy their central purpose in life as they see it. Do not underestimate the potential ferocity of their reaction; do not underestimate the influence her parents may have on her; and do not underestimate the obligations she may have to her family. In Chinese culture, family dwarfs love in importance. And in China, what makes a fantastic boyfriend may be very different from what makes an acceptable husband.
Bottom line: you may know the dynamics of your relationship with this girl intimately well. But if you do not know the parents, you do not know the girl.
Of course, this is all based on generalisations, and no country I know of can so confound expectations as China. But, whatever you do, take things slowly and make getting to know her parents a priority. I hope your relationship is more successful than mine was, but please keep in mind these tips from one who's tried.