[tyciol]

If you plan on something like that, it is best to not interfere with people, like find somewhere you won't get in their way, do not play too loudly, make sure your playing is good, and don't actually ask for money, just have a hat/case on ground.

Even with this, some people are irritable and may report you to a policeman. Some policeman may warn you first not to do it, though possibly a mean one or having a bad day or doesn't like the look of you may say it is a public disturbance. I am not sure what the penalty for that would be.