We just stayed at POR in June and for the most part had no trouble with the buses. Of course, we were going to the parks around 9:00-10:00, so that might have made the difference.
We were in Bldg 37 which is very close to the North Depot and right next to the Mansions (4th stop). Sure the buses were standing room only at the park closings, but so were all the other resorts. One bus would just pull away and another would be there within 5-10 minutes. Sometimes another bus would pull up before the first one finished loading. Very rarely did we have to wait more than 10 minutes for a bus (maybe once that I can think of and that was to a waterpark-15 minutes tops), and we were there for 10 days.
If you are worried about standing, I would go to the South Depot like Jaguar9748 suggests, especially if you are going at the busy times.
I've stayed at values, moderates and deluxes, and I've had bus problems at all of them. Once we had to wait for a bus to one of the parks for over 40 minutes at ASMO and it wasn't during a busy time of day either. AS also share buses with all 3 resorts and I've seen standing room only on them when going to the parks.
I'm not sure why we were so lucky and didn't have the problems that others experienced. Maybe they had more buses running when we were there, because there were too many complaints in recent months, or maybe it was because we weren't going first thing in the morning.
Good luck with your plans.