I have had this bit of fun with phone solicitors who ignore the fact that I am on the "Do Not Call" list. Say yes to everything (without giving them any personal info of course). Yes, I want my carpet cleaned, yes I would like you to do every room, yes I have a huge house with a lot of rooms, yes I want your super duper fantastic package that does it all... yes I will buy the best you have... etc.
Sometimes they figure it out and hang up on me; otherwise when it comes time to give them my personal info I just say "not really, I'm just wasting your time like you are wasting mine." I was getting these carpet cleaning calls several times a day until I started doing this from "Diane" -- since I started doing this so far I seem to be off of their list.
I've also pretended I am going onto my computer to give them all the personal credit card info and stuff they are asking for, and asking them stupid questions.
Of course you would have to adjust the "play stupid" approach since they are there in person... but something like this might work with the meat truck people too.
http://www.youtube.com/watch?v=33BCEPMGggU