Funny because it's right or funny because it's wrong? I've never been to San Antonio but I think Venice is an unbelievable magical place, one of the most remarkable places i've ever been--but I totally struck out on food there.
I love Venezia but I can also get a laugh out of someone comparing it to the riverwalk. It's a cynical take on Venice which I can see an argument for if you make the case that it's just a bunch of tourists plodding around sewage. Please don't feel compelled to defend the city, I love it. I would move there if I could live comfortably, but my opinion is that it is a pretty good joke by Bill.