It is a good idea to power the street lamp with a solar and wind hybrid system. When choosing a proper wind turbine for a such usage, you must concern the 3 points more.

1, The weight of the turbine. A heavy turbine must need a stronger pole to support. And also, the pole will swag more when a heavier thing on the top of it.
2, The vibration. The most annoying thing of a rolling machine is the vibration. It will cause much trouble. Just think about the car tyre... Even more, the vibration of the windmill will loosen the fastening of the lamp or the pole and makes dangerousness.
3, The efficiency. Most street lamp are erected in the downtown area where is seldom large wind but have to be bright. It need a windmill which can start up in a low speed and work well in a low average wind-speed.

At last, maybe, you need some cute and quiet windmills to decorate the street.