A "UV light" would scare away the masses since they think that all UV causes skin cancer. Besides, normal lights do perfectly well at lighting up reflecting signage much further than the light actually projects. UV light generally passes through the air with no problem (I use a UV laser at work) but you may find some weird compounds that fluoresce under UV light. Maybe some fertilizer or something. I don't really see an advantage of using a UV light over a normal light. I don't think the fluorescence caused by UV would be strong enough to see outdoors from any distance. The orange tinted glasses that come with UV light kits are used to block a bit of the visible light out to make the fluorescence more visible, therefore it's doubtful that you'd see it without such a device. Also the light sources that CSI investigators use are tuned with visible and IR bands to block out background noise from normal clothing/sheets etc.

The main problem I see is that the visible light from your normal light would make any fluorescence that you see nearly invisible.