70 degrees. hmm, I'd say it depends on the month.

If it's May, arm and leg warmers, to be removed if the breeze ever dies down.
If it's July, shorts and jersey, because it'll be 85 soon.
If it's January, a swimsuit!



Seriously, it does depend to me what the ancillary weather is like - breezes, humidity, temps rising over the ride or not... but all things being equal, 70 is about the perfect temp here! I don't like to ride much higher than the low 80s.