whenever i'm in beechview (this has only happened about three times), my preferred method to return is to head down crane to 51, take 51 left and ride on it all the way to the west end circle. this is not for the faint of heart, as you have to be able to confidently take up an entire lane of traffic to be safe, and people just blaze through there (it's a 35mph). once you get closer to the circle, there's a decent shoulder without TOO much debris in it. and traffic never seems to be unmanageable through the circle. from there, take a lane on carson until you can get to the trail (the first station square entrance coming from the west end).
takes me maybe a half hour, i want to say. it also depends on the traffic around the circle, as i usually just stay in line at that point (i'm also never in much of a hurry when i'm there). saves you the trouble of going up and over mt. washington, as long as you don't mind riding in traffic.
another way might be, if you're allowed to take your bike on it, to take the transit downtown and then just ride to oakland from there. no idea how long that would take. i'm sure someone has a better method than mine, anyway, that's just how i do it.