Palomar - KCRQ
Great airport, great facilities (good runway and ILS). I stay in Coronado when I visit San Diego and find it well worth the hour's drive up to Palomar (past Montgomery where I have found attitudes and procedures for transient rental pilots less than welcoming).
I've rented from Orion Aviation on many occasions (most recently this May) and would highly recommend them. Their Duchess is slightly ropey but their other aircraft are in very good shape (they have some new 172s and a fairly new model Archer).
They had a very professional attitude towards maintenance and service, which I particularly appreciated (eg staff would come around to top off the oil and clean the windows every morning). The place is owned by a mechanic (Pat - ex USAF who spent time at Lakenheath) who took reports of squawks very seriously and rectified them quickly (they have their own maintenance).
They were also very flexible with me taking a plane all day.
Other than Civic Helicopters (another very professional outfit), I haven't used any of the other places at Palomar.