It might be worth mentioning your concerns regarding the proximity of the barbecue to the hedge (in a casual, pleasant manner) to your neighbour. However a properly looked after barbecue shouldn't present any great hazards to passers by in the street.
I live on a cul-de-sac for traffic, but (because there's a footpath at the end of the road) it is a through route for pedestrians. Every few weeks,at this time of the year, the families at the end of the road find an excuse for a party. It might be because one of their kids has a birthday, because one of the grown-ups has a birthday or simply because they feel like it. (Last week they just put up big 'Street Party' signs). When they do, they'll often have several gas-powered barbecues actually on the footpath, on the grass verge or on the road. There will often be several bouncy castles and a disco as well, with little kids running around until midnight and the adults carrying on the party until 1 or 2am. While it can be a bit noisy at times, I've never had any concerns over the safety of what they do.
Chris