I've been in Buckman for 2 years, eastside for 2 1/2... no car the whole time. Its definitely doable; most of my friends are also carless. Bus service out here is great, I can take 3 different frequent buslines to downtown, or bike 5 mins to the Hollywood MAX TC.
SE really hasn't yuppified; anyone who says that desperately needs to get out of PDX to get some perspective! I think there are a lot of students and very young people (18-21), punks, hippies, etc, who equate having a job with being "the man."
That being said, 28th is da shit