Buried at the bottom of this Metro press release
about the grand opening of Highland Park's new farmer's market is a handy index of L.A. markets reachable by Metro rail (would that there was a Ventura Boulevard line with a stop at the Studio City market). Don't know how easy it is for other areas, but I can vouch for the ease of taking the Red Line to the Hollywood market.
During these trips I've collected a great deal of anecdotal evidence (peeps with empty net bags getting on at Vermont, and women with handfuls of fresh flowers boarding at Vine) that suggests that I'm not the only one who likes to take the train down to Hollywood on Sundays.
Hell, even without the market it's a worthwhile trip: walk down the Boulevard to check out all the lofts under construction, grab a cup of coffee at Caffe Etc.
, then over to Amoeba, or down Vine to browse the freakiest Borders in L.A., or to the Arclight for a matinee (only $11!). Or, best yet, if you're rolling with fat pockets (and you're - ahem - a geek), head over to EB Games to drop some hard-earned cash on a game. Cap it off with a visit to Kabuki's sake bar, and you've had yourself a pretty full day in L.A.'s most urban environment - all without worrying about where to put your L.A. ball and chain (i.e., your car).