TrollumThinks: HK (and Macau btw) is considered to be leaving China from a visa point of view - ie you would need a dual/multi-entry visa to go and come back. (so I guess you can't this time).
I loved HK the first time I went but that was before I'd been to the mainland.
Still - there's lots of stuff to see in mainland China.
Think some of that stuff is historical in nature. It's only been like 12 years or so since HK's lease expired and was returned to China.
TrollumThinks: Guangzhou is a big city - very crowded - and has every kind of food (I mean they'll eat pretty much anything and also there's styles of food from around China)
Edit2: Guangzhou has changed a lot over the last 9 years (and more but I've only been here 9 years) - become more 'international' so you have to hunt around for the old buildings and local stuff. There are many smaller towns nearby though with lots to offer.
Chaozhou is also in Guangdong Province but quite a way to the East from Guangzhou. I've been to Shantou (near Chaozhou and of the same cultural background). ChaoShanese is a different local language to the Cantonese and you'll find some of the older people there don't speak Mandarin. Mostly you'll be ok in the cities and there's always pointing emphatically to get your point across ;)
I always get a bit confused with the language, unfortunately I can't actually write more than a very small number of marginally useful characters so I'm going to be counting on a universal translator to augment my charades.
TrollumThinks: I'd recommend Xi'An to the north too (Great food, nice city, wonderful cultural sites to visit both in the city and out at the Terracotta army bit).
Edit: and if you like spicy food then pop across to Hunan.
Side note - from Yangshuo there's an overnight bus to Guangzhou - 11 hours - not comfortable and only for the strong of heart (those mountain roads with the drop-off aren't safe at night). There's an overnight train from Guilin (13 hours) that's better (or just fly).
TrollumThinks: I've done long trips on the trains many times but that's fun.
Longest bus I've done is 11 hours back from Yangshuo - not fun.
Hope you have a smooth trip at any rate.
I haven't decided where I all want to go, but I've decided not to go see the Great Wall unless I happen to be in the direct vicinity for other reasons. Of all the things there are to see in China, it seems to be one of the least interesting.
PandaLiang: One thing to notice, when we talk about Mainland China, we usually mean China minus Taiwan, HK and Macou, but I don't think you will need a visa to visit HK as long as you are not staying for too long. Maybe one way to do it can be landing at HK, do some visitting, and then enter Mainland China from HK. (I think some of my friends in Canada do it this way, but maybe you will want to consult the official a bit more)
Check this link:
http://hongkong.usconsulate.gov/acs_hkvisa.html OK, so I wasn't going mad there. That's more or less what I had heard previously, but there was some discussion about what exactly that meant.
I guess worst case scenario would be that I headed to HK on my way home. Hop a plane to East Timor for some scuba diving and then do a tour through Malaysia, Indonesia and hopefully, Thailand, Cambodia and Laos in whatever order makes sense.