although i'm from san jose, i don't know whether there are any regular/weekly rides up there. i don't really see anything regular posted on sjfixed other than alleycats/special rides/events. there's also the sj bike party (kinda like midnightridazz) that takes place on the 3rd friday of each month i believe. there are a lot of scenic routes though, maybe a search on bikely or mapmyride will turn up some results.

as for LA, there's midnightridazz for chill social rides, and there's fixed gear rides on LAfixed. many of the LAfixed weekly rides are also posted on MR, though, so definitely look at the MR ride calendar. pay attention to the ride descriptions though, as midnightridazz is really a website for the LA biking community and there are lots of different types of rides posted on there. wolfpack hustle is an awesome ride if you're strong enough of a rider. WPH is monday night 10pm at tang's donuts in silverlake. another ride i regard highly is the Passage of a Few People Thru A Rather Brief Moment In Time. they meet wednesdays 8:30pm at california donuts in koreatown. it's more social but the pace is faster than a typical MR party ride. there are also a couple of good, med-fast paced weekly rides in hermosa beach, cerritos, and long beach, but it seems those are a bit out of the way for you.