I've never seen street performers outside of Carnival activities/parades but unless someone else can give you a definitive answer, I'd say not to chance it as I have a feeling that the VIPD may frown upon it - and if you were thinking of doing it for some type of remuneration (i.e. a tip bucket) they'd be all over you for not having a license.

A few places have open mic nights if that would fit the bill.

Please, please, please no mimes *-)

Granted, I don't live there but the only street performers I've seen are the guys who look to the left before stepping into traffic. I've seen some move real fast and also saw some who didn't move fast enough.............. even tried it once or twice myself but didn't see much of a future in it.