Just to chip in my thoughts on this, since I've both visited OG and played in several SoCal PDGA events. The following are the definitive resources on California tournament activity that will render courses closed and unavailable for play:
http://www.socaldiscgolf.org/2009Schedule.htm - List of all 2009 SoCal PDGA events
http://www.norcalseries.com/schedule.html - List of all 2009 Norcal PDGA events
http://www.pdga.com/tour-schedule - Master list of all PDGA events
The Wintertime Open has been listed on the SoCal and PDGA schedules since late December. Whenever I go road-tripping, I always make sure to check these three resources to ensure the course I want to play is available- I learned the hard way like you, when I only checked the local course website for the course in Santa Maria, saw nothing listed, then showed up to a course full of tournament players.
Also, the Wintertime Open in particular takes the regular OG layout and goes bonkers with it, playing safari from one tee to another basket, temp holes, the whole nine yards. Which would explain why players kept popping up out of nowhere, or coming from what seemed to be the wrong hole.
They definitely should have posted a sign at the course entrance to let people know that there was a tournament taking place, however, that's negligence on the part of the TD(s).
Now, to your other point- I have played about 4-5 PDGA events up here in Norcal, and 4-5 down in SoCal. I play Advanced Am, and I can back up your assessment about the attitudes of players in that region. Obviously I'm generalizing, since I've played with only 20-25 different am players down south, but the prevailing attitude is one of hyper-competitiveness, aggressive behavior, and victory above all without consideration of their fellow man. There are certainly a number of folks down there who I enjoyed playing with and embodied a positive competitive spirit, but it's nothing like Norcal, where the majority of players I've played with are positive and encouraging.
I think what best sums up what I'm describing is- in my tournaments up north, you regularly hear other players on the card vocally wishing your shots well - "miss that tree!", "get in there!" - and congratulating one another on a shot well done. In my tournaments down south, I've mostly seen steely silence.
When I visited OG on a weekend about 3 years ago, it was busy but not totally packed. The locals seemed friendly enough- I think that's less the issue than the tournament players(most of whom are not OG locals) simply being aggravated that there were "casuals" interrupting their rounds. I don't condone the sorts of things they yelled at you guys, but I see that up here in Norcal as well- nobody likes to be in the middle of a tournament, focused and ready to move to the next tee shot, and then have to wait for non-tournament players.
Anyway, in my opinion you didn't miss out on much by not playing OG in its fullest- there is some historical value there, obviously, but as a disc golf course, there are several other courses in the greater LA area that I think are superior - La Mirada, El Dorado, Sylmar, even Whittier Narrows...