I walk up to a group of 2-5 people and say, "Hi there. You look like interesting folks. My name is Christopher Strange, I've been asked to entertain the guests today. What's your name?"
Catching them off guard works well for me hahaNotice he didn't say "I'm a Magician." Sometimes it is great to catch them off guard. Some may assume you are a comedian, or a musician, or maybe even just one of the guests. You could introduce yourself, ask to be invited into the group, then surprise them with magic!
Going up to every person, most of whom were clearly busy, and trying to get them to watch a trick makes you look like a little kid tugging on everyone's pant leg so they'll watch you play with a plastic finger chopper for the nine thousandth time.
Also, also note - Dude face says "I rarely get nos, because I turn nos into yesses" - except he's getting shot down left and right. He's not willing to accept that he has flaws and weaknesses that need to be fixed to make a performance worth watching.
Which is why I so frequently say that performers need to learn social skills as well as tricks.
I got the feeling most people were saying no to him and not to magic in general.
The great thing about starting with a conversation is that it allows you to feel out the group, first. Are they receptive? Are they closed off? Chatting a moment or two before launching into a demonstration or trick means you won't be forcing them to do something they don't want to do - then everyone likes you, even if you haven't performed for them.