When you find a winery that claims to produce a "California Champagne", that is almost always a big red warning flag. US Wineries are legally allowed to use the term (much to the chagrin of the French). From the Wikipedia entry on http://en.wikipedia.org/wiki/Champagne_(beverage)|Champagne:

• While most countries have labeling laws which prevent the use of the term Champagne on any wine not from the region, some – including the United States – permit wine producers to use the name “Champagne” as a semi-genericname. One reason U.S. wine producers are allowed to use the European names is that the Treaty of Versailles, though signed by President Wilson, was never ratified by the U.S. Senate. The Treaty of Versailles included a clause designed to limit the German wine industry and to allow the use of the term Champagne only on wines from the Champagne region of France (which had been in the middle of numerous WWI battles). As the U.S. Senate never ratified the Treaty, this language never was implemented in the United States.

Any winery that produces a halfway decent bubbly will refer to it as aMéthode ChampenoiseSparkling Wine, indicating that the carbonation was generated naturally in the bottle. Wines labelled "California Champagne" are almost invariably produced using the Charmatbulk process. And while there's nothing wrong with that in principle, in practice the wines usually turn out to be of poor quality or generally unremarkable. Since there are plenty of good quality Sparkling Wines that are readily available at retail for around $8-$15, avoid anything that claims to be "Champagne" unless it's the real thing.