Yes, the State may dictate a minimum Bio content, but any distributor/producer can "dilute" their diesel with a higher %. It's another reason to be in the habit of prepping for refills at the half tank point. If all you come across is 20% you have leeway to wait.
Also note that many providers offer more than one grade of biodiesel, and you may have to check more than one pump if they aren't signed obviously at the island approaches... kind of pita. Here is a site that can help a little if you click-check only the B1-B11 box at the bottom, but the site is kind of clumsy, and is better if you already have a station and its name in mind, but need to know if they have lower level biodiesels:
http://www.brevardbiodiesel.org/map/bd.html .
Also, on reflection to earlier statements, low sulphur diesel was used as a misnomer; since June 1, 2006 diesel sold in the US and most of Europe has been ULSD, Ultra Low Sulfur Diesel.
Pioneer Fuel told me years ago the Pacific Pride franchisees of course met the minimum state Bio content regulations, which for many is 10% or less, and then if facilities have extra tankage, they'll offer multiple grades. It's easy enough to check the blends available at any PP facility by going to their website. Conceivably that's possible with any large-enough fuel chain.
The local PP I frequent sells 5%, but doesn't appear on the above linked site, so it may not show card-lock providers. CFN and PP are owned by the same company now, and I hope they both continue clinging to the state minimums, as they'll possibly issue a card common to both, expanding available locations for members.
Joel