The group known as SaveJFC.net said it plans to take out a full-page ad in The Hollywood Reporter to make sure the cable network hears its message.
Fans also have launched petition drives, made countless phone calls, and sent emails and letters sent to HBO executives.
"The show hooked me from the beginning with its offbeat dialogue, brilliant performances and breath-taking surfing footage," explained fan Brian Lowery.
Martin Bradburn added that occasionally "a show comes to television that breaks the mold and expands the genre into uncharted territory." He called the show "a radiant tapestry of the human condition with all its hopes and failings."