PORTLAND — Self-consciously quirky, outrageously liberal, Portland feels a bit like a hippie museum. On a recent, glorious Sunday, in the hipster Hawthorne neighborhood, white-bearded bikers in bandannas straddled their hogs in the sunshine, crowds of middle-aged, Birkenstocked customers strolled in and out of what could only be termed “head shops,” while others flipped through racks of vintage clothing — everything from old Simpsons T-shirts to velvet blazers to flowered hats from the '50s.