Can I apply for a new (L)visitor's visa for next China trip while I am still in Guangzhou ?

Hi,
I am holding a Canadian passport.In this June , I obtained a (L) with double entries expirying end of Dec 2013. I had visited once in July and I am now re-visiting Guangzhou. I want to visit other Asian countries this month. But, after that, I am planning to come to visit other family relatives again before end of this year .
Can I apply for a new( L) while I am now still in Guangzhou ? And if so, what document are required and how much time do I need to wait for this new one ?
Thank you so much.