Didn't that Breakaway ride also do Oakville grade (the bad side - east to west)? That's about the worst in the area.

V's right about King' Ridge and Coleman - and that the SJ ride probably won't require anything different in your gearing. That course is pretty flat, all things considered. as for Levi's - KR is longer, but Coleman comes later in the ride and thus feels harder than it is. You would probably be happy with a compact double on those - if you have a standard double now, you would have to replace the crankset/FD I think.

Here's another thought - not ideal, but I do know that some of the bike rental places here rent decent road bikes (Kestrel, Marin), which would come with a triple or compact double. Do you really want to change the gearing on your bike if it works for what you usually ride at home? I know the sustained climbs are no fun on a standard double, but changing everything just for a few rides - even if you come back and do one ride every year - seems like a bit much.