If you do go busking I'd HIGHLY recommend sticking with backing tracks. if you go without you will feel so naked! Every squeak, every hesitated note, every bum note will be out there for everyone to hear. In reality, no one will notice these things but it will be magnified in your own mind, that everyone is looking, everyone's a critic and everyone thinks you're awful lol
If you go with backing tracks "The Band" will be a big support to your act, if you lose a tune, or where you are (and you will because your nerves will make you go wrong) then you can listen to the tune and it'll help you get back on track.
It's an amazing experience whether you do it for the cash, the compliments or just the practice just do it, don't think about it, just do it!
Don't forget though, you will have an audience right here who will want to know how you got on, me especially!