Los Angeles, CA
Jankovich & Sons, LA Harbor, San Pedro:* 500 gallons @ $4.35/gal, + 8.25% sales tax.
These folks don't quote prices over the phone, but they're consistently the least expensive I've seen in all of Southern California.
I also heard a very recent report that Coral Marina in Ensenada, MX is at US $2.40/gal... if they have fuel.* Apparently a lot of San Diego based vessels are making stops at Coral on their way south to fill up.* Pemex (the Mexican national oil company) countered by limiting supply to the fuel dock.