If you have a three or four weeks vacation, I recommend you go to Yunnan,Guilin, Chengdu,Yangtze River(available from Mar to Nov), Xi'an and Beijing. Do not take train journey all the way, cause it's too tiring. Take flight on long journey and take overnight or day train on a short one.

Public bus in China is very convenient.If you take public bus just inside a city, the cost is always within rmb 5 yuan.Also taxi service is available in all of the cities.

Price for meals are depends on. Dishes in the small noodle houses and restaurants are cheap(it costs around 20 yuan/pp for a meal)

More information you need to know if you come to China, go to the below links