Table set up, Netbook, make sure to have a friend around you to just be there with you, as the reality is you'd be trying to be a mobile bank, which to me makes for a super awesome target.
I would do this near a police station or something that has traffic pass through, but is not necessarily the most high traffic area (I only worry about idiots who would have that mentality of 'ah.. mobile bank, let's rob him').
Maybe the ideal solution would be yourself and two friends, those two could be buffers with information and helping explaining for anyone who would actually get to you for the final transaction. Actually, this seems really optimal and far more trustworthy than one person with a sign. Good luck, sounds like a fun day out.
Thanks for the good wishes.
I would mostly be on the street in the picture. It really is that busy during a regular day. Realistically it would be just me, alone, walking around with a sign in that same area for a few hours during the day. I'm not expecting to be pulling in $5,000 a day I would be surprised if I even got up to $100 a day (turnover, not profit).
It would be best for a regular store owner to do this as a sideline, and I imagine in 6 months or a year or two years there will be plenty of stores doing this, just like you see (or used to) signs saying "faxes sent here, $1 a page" when it's not the guy's main business at all.
However, the parameters are as I said. Just me, alone, with a big sign in a busy pedestrian area in the UK, no sign of gangs anywhere!
I'm looking for info along the lines of don't use the regular bitcoin client but use six instawallet accounts, or whatever seems advisable to people who are much more familiar with what's available than I am.