After completing my journey, I wrote a report describing what I found. You can read an HTML version of the report here (complete with lots of graphics), or you can just read a really brief summary:
The vast majority of rock music in China is in Beijing. In fact, I was told many times that the only rock music is in Beijing, though that is not strictly correct. Beijing's dominance seems to be primarily a result of the large number of foreigners in Beijing, since about the only way for a struggling band to make money is to perform in Western-style bars.
There are many rock bands and musicians in Beijing, the most famous of which is Cui Jian (who, ironically, isn't allowed to play in Beijing). All of the people I spoke with felt that the situation is improving and it is likely that rock music will soon spread to other cities outside of Beijing.
Some Chinese rock music is available both inside and outside China on tape and compact disc. Both as a form of research and because I like listening to it, I have acquired several of these CD's, and have sampled a few bits of music. If you'd like to get an idea of what Chinese rock music sounds like, visit my online music samples page and see what musical treats I have available this week.