Most of the veggie vendors come up from the Lucerne Valley and have some great stuff that varies every week, but most things will reliably be there every time. I go every Tuesday to get my lettuce, kale, and other veggies for the week. The prices are moderate.
There are also local vendors selling everything from garden gnomes, to clothing and hats, to tupperware. More like a flea market/swap meet/farmer's market than a pure farmer's market.
Some great hummus vendors there too!