I grew up at a different winery a mile away, and I can say the only winery I can think of with a "tasting room" is Pride. Barnett, Paloma, and perhaps Schweiger will all have fantastic views from their 2000' elevation facilities down to the 300' elevation valley floor.
Having grown up there and knowing many of the older producers, you'll have a much more authentic experience somewhere without any real tasting room. There will be a good chance an owner, winemaker, or both will be around to pour and discuss what they do, and you will either do the tasting in the winery where you can get a feel for how wine is made, or out on the lawn if it's a nice day.
None of the wineries at the top of Spring Mountain with the possible exception of Pride will have tour buses or even large limos.
Do your research ahead of time as to what varietals different wineries produce, since a winery like Paloma focuses on making exceptional Merlot and probably doesn't make any whites.
Yes. We were there last weekend.
The wine, especially the Rattlesnake Hill, was very, very good. We went to several wineries in Spring Mountain that day, and Barnett's Rattlesnake Hill was at or near the top.
The place - despite the website - isn't fancy at all. You just belly up to a very small formica counter surrounded by wine barrels.
Another place to try nice wines is just down the road less than half a mile: Berhens & Hitchcock. They also have another label, Edna Schine. Very nice wines at a remarkably good price valye, and good people. The owner, Les Berhens, was kind enough to sit down and talk with us for quite a while (he wasn't our guide, he just wandered by) Robert Parker "found" Les Berhens and named him something like the best new winermaker in Napa a few years ago.