I do contribute to people like Open Door Mission, so I'm not going to be bothered by all the spare-change types all over then street. I never carry money, and never have "spare change", bit I don't feel the need to explain that to any of them.
There's a Walgreen's on Montrose Blvd (Houston's answer to Castro Street) near where I work in Houston, and bums frequently hang out there (some appear to be teenage runaways who did not do so well with the male prostitution thing). I went in there one day to pick up a prescription, and some lady was hitting up people in the parking lot. I ignored her and went in. While I'm in there, a lady customer is haranguing the poor manager of the store for allowing panhandlers out front to make her uncomfortable. Instead of chewing that guy out, why didn't she tell the drunk outside to get lost? I constantly see people ream out the proprieter of an establishment for "allowing" bums outside, but they don't dare tell the bum to take a hike.
I growl at them. I mean, literally, bare my teeth and growl. You'd be amazed how quickly they leave you alone.