Sunday morning and Humboldt Boulevard, usually dominated by speeding metal boxes, is filled instead with smiling faces: tots on trikes, parents with strollers, joggers, bladers and every kind of bicyclist. It&rsquo;s like a more family-friendly Critical Mass, minus the pissed-off motorists. Are we in some alternate universe? No, says a green-skinned alien who&rsquo;s waving to [...]