Since arriving on Monday I’ve seen a lot of bands. Walking down 6th Street will do that. But it seems that during the set of every good band I see, I’m asked the same type of question by an interested member of the audience: Who is this? Do you know who this is? What did they say their name was?
Mumbling your name at the microphone is at least a better idea than not saying anything at all, but still, the amount of fans you will be able to keep after a SXSW show will be much greater if you have your name on display ANYWHERE. On the kick drum, on your amp, on banner behind the band. The easier for you to set up, the better it will be, but expecting to have the venue properly poster the line up at the show is a fat chance.
Make your life easier and have your bands name somewhere, anywhere, at your live stage show. It will do wonders, it will get you fans, it will translate to cash! Be creative in your sign and just do it.