The one and only time I went to Puerto Vallarta my sister taught me a trick that has worked for me everywhere. Instead of ignoring the peddler I look them right in the eye as they approach and very slightly give a no nod. As she said, once they engage you in conversation you are stuck.
It works really well here with all the Guatemalan people on the beach. I find them more offensive than the time share one as so many people come here and think they are buying authentic Belize art work.
As a member of the Chamber of Commerce I have to report that this issue is addressed on an on going basis. Time Share people are not to be more than 10 feet from their booth.
AmbergrisCaye.com 
