Cyclesick....Mercer has been that place for me thru 23 years of marriage and 3 kids, so you are in the right place!.... and you can pick up your karma points at any of the trail days - rode there for years before I even knew there was a jorba trail crew working there and I still don't go to maint as often as I want to for all the same reasons you had, but I go when I can....all my cycling partners these days came from trail maint at Mercer too.
That being said, I am going to try and join in on the 17th....
Oh and since this is the conditions thread, the main trails at MCP are rideable until the rain hits later today....I was out last night and there is plenty of dry trail there at this point....guessing u got up until about 2pm today before it rains....