I ride my folder (Dahon Speed 8) at the beach regularly and I run in other people with folders. Just today I was biking around the Rose Bowl in Pasadena and ran into a person on a Bike Friday. A few weeks ago I saw a dad and son riding a tandem folder. But yeah, I do notice that folders are more popular in areas with subways as a form of transportation. As for being in Los Angeles, it's not as common.