Riding the Springwater trail is far, far better than riding across the Sellwood Bridge. Just cross at the Hawthorn Bridge and then ride up Broadway to PSU. You'll have plenty of company along the way.
I don't think the Springwater is anywhere as bad as it's being made out to be. I've been commuting on it almost every work day since it's been open (and commuted across the Sellwood Bridge for years before that) and have never seen (nor heard of) any problems. While there are homeless folks along the trail, there are far more commuters and runners out there. The most dangerous part of the commute is when you get around all of those crazy cars!