I have committed an excursion to Temecula wineries:
Callaway
2008 Bella Blanc Sparkling Wine - It is described this way: "This sparkling chardonnay has a fresh bouquet of peach and exotic melons with light caramel and toast. Soft apple, Anjou pear, and a finish of crisp orange zest;" yes to the first sentence, no to the second; ordinary
2008 Special Selection Rose of Sangiovese - again, a very ordinary, slightly sweet rose
2004 Winemaker's Reserve Dolcetto - here's something dry and crisp! it is a little too extracted but it hints that, maybe, someone who worked on it knows what a chianti is; worth a second try
2005 Winemaker's Reserve Cabernet Sauvignon - lots of wood, not overtly perfumey but conceals the wine
2008 Special Selection Nebbiolo Bello - a slightly sweet rose wine; eh
2008 Special Selection Muscat Canelli - peachy-lichee, very aromatic; great for non-wine drinkers (like my partner)
Mount Palomar
2007 Dry Riesling - has seen some oak so it's very odd; finishes thin
2007 Castelletto Cortese - viscous, with a bitter finish; amazingly, my partner liked this one
2005 Cinsaut - crisp, dry, light, even better with a little chill on it, worth trying again
2005 Castelletto Sangiovese - some good fruit here but smothered in the barrel; it's not that it tastes of oak (it should, after 24 months in new oak, but it really doesn't overtly) but it is tired and burdened with a lot of non-fruit flavors; a shame to do this to otherwise nice fruit
2004 Syrah - lots of wood tannins, all furry on top of the extract; not much varietal character
2006 Riesling - 3.5% RS; limp, flat
Baily
2008 Dry Riesling - thin, bland
2008 Montage - sauvignon blanc 66%, semillon 34%; taste pretty much like a s.b. varietal; could be OK with fish/shellfish
2006 Sangiovese - a young, fruity wine with no particular character
2005 Cabernet Franc - varietally correct but no interesting soil tones
2003 Port - cab franc, 18% alcohol, 11% RS; very walnutty aroma, blueberries, not overpoweringly goopy
So, there is it. Pretty much like folks said it would be. All these places had bars big enough for busloads. The clubs are designed to make it easy to sign up and painless to keep participating (e.g., buy 2 bottles to get a membership, the club sends 2 bottles every 2 months). It's a triumph of capitalism, if not oenology.
The pourer at Mount Palomar made two interesting comments. The first: When I described what I was looking for in a red wine -- dry, minerality, good acidity, not too much wood -- she flat out said that they had no wine that fit that description. Points for honesty. The second: When we asked her about the apparent fascination with grapes that hardly anyone else in the US grows, she said that Temecula, until very recently (roughly 5 years) had been in the hands of hobbyists... older men who, in their retirement, wanted to make some wine that reminded them of their homes, whether the valley was good for those grapes or not... but that professional winemakers were starting to move in and are starting to change how things are done. Good story, anyway.