Student Visa

I am travelling to China for an exchange. However, the chinese university has sent out the visa papers late, which means that it may arrive in my country very close to my flight date. Is it a MUST to carry the student visa with me when I enter the country, or can I travel visa-free for 15 days and then arrange for the visa to be delivered to me? I can exit mainland china to Hong Kong before the 15 days visa-free period ends and return back to mainland with the visa papers if necessary.