I broke down and bought an Oakley M-Frame with three lenses. I use the clear at night, amber in low-light conditions, and dark grey when it's sunny. I tried some safety glasses, but they fogged too easily. The M-Frames fight tightly around my eyes and are nicely vented. If they fog at all, it's gone within seconds of when I start moving. Plus, the higher quality lenses do make things clearer than he safety glasses I tried.
But safety glasses are so cheap you should try them first.