Now you are starting to make more sense to those of us who live here in the heat and sun. I understand the allure of a convertible for a "California road trip" but quite frankly, a convertible in August in either the heat of Death Valley and the Mojave Desert or the altitude of the Yosemite high country would be miserable. A friend and I did it many years ago when we were young and stupid and the wind- and sunburns were epic. Trust me on this. For long driving days you will be far more comfortable in the shade and air conditioning of a full size car or SUV. Just be aware that the SUVs are real gas guzzlers and the cost of gasoline is skyrocketing right now. Coming from Europe, the price likely won't surprise you much but the sheer quantity of fuel you will burn on this trip will be amazing. An SUV will only exacerbate this.

As for deciding how to get to/from Yosemite, I have to say that the Tioga Pass route which traverses the Park east/west via State Route 120 has some of the most spectacular scenery you will see on this trip. It is best while driving west to east but almost as nice in the other direction. If you want to do some of your driving in a loop rather than backtracking, I'd suggest either heading north on SR 395 after crossing Death Valley and then cross through Yosemite Park on your way to San Francisco. Alternatively, if you go from San Francisco to Yosemite, you can traverse over to the east side and drive south on 395 to get back to Los Angeles, avoiding the San Joaquin Valley route back south. It would only add a few hours to your total drive time and that whole stretch of SR 395 from Yosemite to the Mojave is truly beautiful.

If I were planning this trip, I'd go LA-Las Vegas-Death Valley (insert Grand Canyon if you must) -Owens Valley north to Yosemite-San Francisco-PCH-LA in one big loop. If you have time to stop along the way after Death Valley, this route takes you right past Mount Whitney, Manzanar, the Alabama Hills, Devils Postpile National Monument, the volcanic area of the eastern Sierra, Mono Lake, Tioga Pass, Yosemite, the Delta country, Napa Valley wine country (a short deviation), San Francisco, Santa Cruz, Monterey, Carmel, Big Sur, the Pacific Coast, Hearst Castle, the elephant seal colony area, Cayucos/Morro Bay, Santa Barbara (more wine tasting areas), Ventura, Malibu and Los Angeles. There would be far more to see and do than you could possibly fit in but you can pick and choose what you like and not backtrack any driving.