John Wayne airport (KSNA) would be the closest to Irvine, but would be pretty expensive. I don't even think they have self serve fuel there so plan on buying elsewhere or almost $8 from the truck. I'm at Fullerton airport (KFUL), which is much more of a GA airport. We have a 9 (mine), an 8A, and a couple of Thatchers under construction, plus a 6, 9, and 12 flying and based here. Avgas is above $6, you may be able to triple up in a big hangar for about 350/mo if all three planes were pretty small.
Further away are Corona (KAJO) and Chino (KCNO), both great GA airports and we'll established experimental communities.
Long Beach, CA