Update: I just returned to the U.S. after a whirlwind visit to Shenzhen and Hong Kong. Maybe we didn't visit the right parts of Shenzhen, but I just can't envision myself living there. We did spend some time in Shekou/Sea World, and I visited a couple of the large shopping centers, but I encountered very few other expats. I plan to study the language, but it will be some time before I can communicate effectively. English doesn't seem to be widely spoken. To me, SZ seemed like a sprawling suburb, and I'm afraid I'd feel very isolated there.
Hong Kong was another story entirely. Although it would be a huge change, I could envision myself living there. We met a few other expats right away, and I could easily navigate the MTR and make myself understood in the shops. And I definitely think there would be more career opportunities for me there.
My husband is at the Shenzhen office for another week. However, he's told the company that living in SZ will not work for us. He comes home for 10 days before leaving for a trade show in Europe. Once he gets back from that trip, we'll see how (if?) the company plans to assist us with relocating to HK. The commute will be a challenge, but he is also going to tell the company that he will only come in twice a week. (He's the creative director and feels confident he can manage his team remotely. He even thinks he can do the job from the U.S., but the company really wants someone in China.)
I realize this may not work out. He's told them all along that he wanted to live in HK, so he is prepared to walk away if that's not an option. Also, he is unwilling to sign the employment agreement they've drawn up. Clearly, there are a number of issues still to be resolved. The company seems to play fast and loose with the rules--one expat who has been there two years never even got an official work visa!
Although I was excited about the prospect of relocating to HK, my gut instinct tells me this may not be the right move for us. We remain in limbo for the time being.
Thanks again for all your input.