There are several good farmers' markets in the San Jose area. One takes place on Fridays right in downtown. It's not the biggest market, but a nice service to the commuters who work downtown as well as local residents. Here is their info: www.sjdowntown.com/eve_eve_far.html
On Sunday there is another market in Japantown, a neighborhood just a few blocks from downtown. This is a good market that has a lot of produce and caters to a larger community than just the Japantown neighborhood. You'll find good variety here. www.japantownsanjose.org/
Another market, larger and in the adjacent suburb of Campbell, takes place on Sundays also, all year long. This is a great event to visit for either buying good, fresh regional produce, handicrafts or some prepared foods. The market covers about three or four blocks in downtown, when the street is closed to auto traffic.
What I like about this market, besides the good produce, is that there are some good food items that reflect the varied ethnic makeup of the South Bay region. Here you will find vendors selling Indian spices to cook with, Afghan specialties and other types of foods along with the more conventional bakery items, seafood etc. that are as fresh or better than anything you will find in the supermarkets.
Santana Row, Winchester Boulevard and Olin Avenue, San Jose; Sun noon-2pm;
Microwaving is easy; slow food takes a little more time and expertise but is well worth the effort. Every week at its Farmers Market, Santana Row hosts guest chefs who will demonstrate the finer points of the culinary arts. With luck: samples!