Unfortunately I believe this achievement is glitchy/unobtainable. I've completed the challenges for Atlanta, Washington, Toronto, Tampa Bay and San Francisco and sadly it didn't pop for me.
I'm going to try a 6th challenge and hope it pops. If not, I hope a patch or update will fix this.
EDIT: Just did a 6th challenge successfully (Boston) and still did not pop. Guess a patch will need to fix this but for now it's unobtainable.