Last night I figured out why I kept flatting at Wildflower.
While replacing my tires and tubes (with significantly better ones acquired at the-shop-formerly-known-as-Santa-Teresa-Bikes), I found a large hole in the rim tape right over a spoke port.
Checked the tube to see of the location of the blowout corresponded. It did.
Sigh. Off to PA bikes to get some rim tape.