I think Wednesday (May 1) and Thursday (May 2) evenings are good times outside the conference schedule. I'm not as familiar with SF compared to others here, so I'm open to suggestions on places to get dinner.
I can make it on Wed or Thurs (with Thursday slightly preferred)... I think the open source security summit is just a related Dockercon event, looks like 10a-noon so I don't think it will collide with evening gathering.
OSHA Thai on 3rd -- asian fusion, fun place for groups, more of a sit-down dinner
Mikkeller -- huge draft beer selection, limited menu, good food for meet and cheese lovers, limited vegan options, no reservations, tho that could be a plus, since it's easy to hang out if everyone doesn't arrive all at once
If we want to go a little farther, two of my fave restaurants, both "french vietnamese"
Thursday is better for me, I have another event on Wednesday at 8.30ish. There are always lots of dockercon events at thirsty bear as its next to moscone so I might be tired of it by then. osha thai/mikkeller/slanted door are all lovely, havent tried le coloniel before...