It's dark out when I ride in, so I just say "g'morning" and usually get some sort of grumble as a response. The other cyclists out that early don't seem to be having any fun. The joggers, OTOH, all give me a very enthusiastic "GOOD morning" right back.
(A side note - this season's new jogging accessory seems to be glow-in-the-dark armbands or an LED blinkie hydration belt! Yay! Fewer ninjas!)
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"I feel like my world was classier before I found cyclocross."
- Mandi M.