I don't think you can really have a designated protest zone where protest disruption is minimised. If a protest is completely non-disruptive and draws no attention because it was pre-corralled away from the press and from anyone whose attention might matter, then it might as well not happen. It's a tree falling in the woods. It is a protest in name only, de-fanged and technically still extant, but utterly without point.
The G20 summit is happening in Brisbane soon. There will be protests, because some people see the G20 as a colossal waste of time and money where big government officials get together and talk about how great they are and how to screw over the dirty little poor nations some more. Ahem. Anyway, they know there will be protests. These protests will be placed inside fenced-off areas specially designated for protesting, far away from anyone who could matter and with an assigned police negotiator to keep them under control. That's not a protest. That's camping in the city, and it means nothing. If you've been pre-handled as a protester, if you have to give advance notice that you will be protesting, filling out forms in triplicate and returning them to the relevant authorities, you're not protesting any more. You're registering a formal complaint within a system that will file it away and ignore it completely as much as possible, even though you might be present in some capacity. It's a farce.
Mokalus of Borg
PS - The best you can hope to do is raise awareness.
PPS - Not in the people that matter, though. Just everyone else who never gets near them.