Not in CA, but AZ: I can recommend the Pima Air&Space Museum and the Boneyard tour, unless that will cost you a divorce. In that case, please stick to the horseback riding plan!
Edit: Closest airport is Tucson
I can only second Harris Ranch – fantastic steaks at their restaurant. Runway’s only 9 metres wide, btw – nicely challenging with the DA42’s 13 metre wingspan. Also you may get a bit distracted during landing considering the cow fart smell from the ranch etc.
Victorville (KVCV) with its aircraft storage / wrecking facility.
Victorville’s pretty cool, both on the ground & overhead…
Other cool desert airports: Mojave and Inyokern.
Looks like we got quite a few SoCal specialists on Euro (sic!) GA!
Second all of the above. Some more could be:
1) San Luis Obispo (KSBP). Nice old downtown and a quick trip by car to some of the more spectacular parts of CA1, aka Pacific Coast Highway
2) on the other side of the San Joaquin Valley you could go to Visalia (KVIS), get a car and drive up to Sequoia National Park, which is spectacular
3) Victorville (KVCV) with its aircraft storage / wrecking facility. Never been myself, so not 100% sure what you can visit, but may be worth considering
4) Napa and Sonoma I think have been mentioned already
5) Santa Barbara (KSBA). Get the crew car (free for 90mins or so) at the FBO and drive up to the Mission. Beautiful, you’ll be in a different world. Or get their bikes (also FOC) and cycle down to the beach restaurant.
6) if you’re into aerobatics (and the airplanes and people involved), go to Santa Paula
Other than that, lunch at Camarillo and dinner at the Typhoon Restaurant in Santa Monica! Yeah!
If you want to see a real collection of biz jets, you could go to John Wayne / Orange County airport (KSNA). Last time I was there the lineman parked my Cessa under the wing of one of the bigger ones….
Enjoy!
I recommend West Valley Flying club. I was there 10 days ago to do some Bay area sightseeing flying myself. They were super flexible in finding instructor + plane on the time slot I needed (I called them less than 48h before I wanted to fly). Before anyone asks, yes I wanted an instructor with me as I didn’t have time to do a normal checkout on a plane and then rent (I have standalone FAA license). In addition the airspace and air traffic around the Bay Area is pretty demanding at first sight. I was in SF for business and only had a short time slot (few hours) available, hence no wish to rent but just to do a proper sightseeing tour of the Bay Area including Golden Gate, SF downtown, Berkeley etc
Unfortunately, the morning I drove down from downtown (25 min) it was completely fogged in… I waited a short while but did not have time for it to lift… what a bad luck!!! I’ll have to do it again next time I go to SF…
WVFC actually have two sites, one in San Carlos which is closer to SF (just south of KSFO apt) and the other one in Palo Alto (which also has a bigger fleet). I’d recommend the closest one in San Carlos – still seem to have decent availability. But give them a call and check.
All the best and good luck! I think you’ll have a splendid time!
Fond memories of California, Mount Shasta is quite scenic! There is a good vibe, the people in the area were super nice, they gave us a few lifts around town and up the mountain road!
Approaching Shasta from the air:
Unloading at the airport (just how much can you fit in a Cherokee 
?):
Climbing Shasta itself:
On the way back to the coast:
IIRC you can find such ranches around Lassen Park. Not ranch strips, but airfields in reasonable distance from places that offer horseback riding in wonderful terrain.
I would venture that you would find such places around Mount Shasta too.
For something really spectacular, you could fly about 200 miles from Vegas to Bryce Canyon, stay at Ruby’s and go horse riding around the national park with some of the most spectacular scenery.
Ruby’s will pick you up from Bryce Canyon airport.
Many thanks for the suggestions. I will investigate them.
I will only rent the aircraft for 6 days. Otherwise the misses will complain ;-) So I need to find a good combination between leasure and flying. Las Vegas is the only fixed location we want to go to. I was actually looking for a ranch air strip, where my girlfriend would be able to do some horseback riding. Unfortunately I was not able to find an airstrip which suits both these qualifications and also offers accommodation. Does anyone know if such a place in California/Nevada exists?
@Silvaire I did my flying training at Gillispie Field. It is indeed very convenient to go to the city center with the tram. Met many nice aviation minded people.
If you want San Francisco land at Oakland not SFO.
I did not include any Bay Area airport since the OP was going to rent in the bay Area. But if I should recommend airports close to San Francisco, I would stay clear of KOAK. Too many people in uniform with over-inflated egos since 9/11. Hayward is definitely an alternative (that’s where I did my IR) – there is a BART station nearby. Otherwise San Carlos or Palo Alto. Walnut Creek is farther but there is BART. Same thing at Livermore.
And regarding Lake Tahoe – sorry – I meant South Lake Tahoe.
Columbia to see the old gold mining town.
I second that. Town is in walking distance from the airfield.
Cambria is a scenic town on the coast
If you plan to visit Hearst Castle – or see it from the air – that would be an alternative to the private strip at Hearst Castle. I do not even know whether it is possible to obtain permission to land there.
Edit: Too bad
I’m currently living and flying from the Bay area, with my aircraft based at Hayward.
West Valley club at KSQL and KPAO seem to have a large fleet and may be able to help. Livermore has a few options as well; the Particles club is good value for regular renters, but may not suit a short visit.
You’ve had some good suggestions already for places to visit. I might add a few others to consider:Columbia to see the old gold mining town.
Oceano and Monterey Bay Academy (closed Saturdays) have good beech access and I’d second Shelter Cove.
Lake Tahoe is worth a visit. S Lake Tahoe is closest though Carson and Minden are easier to access, but you would need to rent a car.
Kern Valley is a beautiful location. They used to rent old american cars. I’m not sure if that’s still available.
When I was based in L.A. my regulars were Catalina, Big Bear, Camarillo, Santa Paula amongst others.
For Death Valley, Furnace Creek has the Fuel and local facilities, but Stovepipe Wells is worth a visit to see Mosaic Canyon and the Mesquite dunes. The Chicken Strip in Saline Valley is great, but the rental people probably wouldn’t like you landing there!
One way or another you should find plenty to fill a week or two’s vacation
