Always have proxies when doing a long list of those or you will get banned for 24 to 32 hours or even worse the Captcha's from hell who never seems to work.
Unfortunately, public proxies are more than likely going to be banned already. If you have a dynamic IP, that tends to work better (although that makes me wonder if it's possible to get a whole subnet banned, enough to piss off a lot of others on the same ISP, and thus put more pressure on Google to not do it or at least give the practice more public exposure. "Man gets city banned from Google by using Google search to do what it was designed for" would be a funny headline...)