Guangzhou is an important city in China, with a great system of transports -– you can easily reach Canton by plane, bus or train (this is also probably the best way to depart to Hong Kong, which definitely deserves a visit).
During your stay, you don't want to miss the chance to visit the Mausoleum of the Nanyue King (one of the best museums in China), Yuexiu Park (a beautiful park with a lot of historical landmarks, and where you will also find the Zhenhai Tower –- provides beautiful views of Guangzhou city), Chen Clan Ancestral Hall, Guangxiao Temple (the oldest in the city), the orchid garden, and the Cathedral of the Sacred Heart.
If you visit this city in summer, you should also visit the Pearl River area, a place full of life and small markets; there are also companies that organize evening cruises to get a different perspective of the city.
There are a lot of hostels in Guangzhou, but they are a little bit more expensive compared to others cities in China. Most Guangzhou hostels are really nice, with all the average facilities.