Well, if we were to assume that the meeting itself got out at 2 (fat chance of that)...
It'd be about a 15 minute walk to the Beaverton Transit Center (I'm saying 2:20), then we'd ride the Green to Pioneer Square, arriving at 2:46. So, in this case, I'd think 3 would be a good time.
However, since I don't think the meeting will get out that soon, we may want to have it at 4.