I'm not sure about fuel discounts but I know that NAC is pet friendly - the former secretary used to bring in her chihuahua mix all the time and I've taken my greyhound in with me as well.
I earned my PPL at this school (currently finishing up IFR) and my instructor has mentioned bringing along all sorts of critters on lessons (he's pretty sure he's the only person who's ever been thrown up on by a bird while flying).
National Air College
3760 Glenn Curtis Drive
San Diego, CA 92123
FBO Office phone: (858) 279-4595