Jeans worked fine for me, 6 miles in, this morning.

60 degree weather combined with moderately brisk riding can have you sweating pretty heavily: my rule is to consider the "felt temperature" when riding to be 20 degrees higher than the thermometer temperature. My ride in was in 40-45 F weather, and lightweight, close-fitting jeans (plus a long-sleeved T-shirt) were great for that.

It would be appropriate to stuff a change of shirt into your bag. Heavy jeans tend to absorb moisture and odors more than lightweight jeans do, so consider that as well.