There are a lot of wonderful choices, particularly if you make some appointments. For a start, just walk down Grand Avenue in Los Olivos. Among others, visit Andrew Murray and Epiphany, but definitely stop by the retail shops which pour a lot of the smaller local producers' products. Los Olivos Wine & Spirits Emporium, at the end of town, is the best.
If you like Rhones, stop by Beckmen.
A drive across Hwy. 101 into the Santa Rita Hills area is also worthwhile. It's open countryside, so things are more spread out, but stop by Sanford, Lafond, Melville and Babcock. I think Fiddlehead has opened a tasting room since my last visit, also, but that may be by appointment only.
Except for possibly Fiddlehead, those are all open regular hours. In Santa Rita Hills, see if you can make an appointment at Clos Pepe. There are also a lot of small producers in the Lompoc Wine Ghetto that will probably welcome you with an appointment, although with limited production a lot of what you'll taste there will be barrel samples.
Have a great trip!