FFGrey,
I just re-read your post, and would like to add a few comments to my reply above.
1. Given your travel date of mid-April, the liklihood of Tioga Pass being open is next to nothing, so you can forget the Yosemite alternative via the east entrance. You could visit Yosemite via Fresno (ie south entrance.) Want an itinerary for that?
2. I support your hunch that it would be better to go to Las Vegas and drive to San Francisco, rather than drive to SF then fly to LV and back again. But note that you will be up for an extra day's car rental (small) rather than return air fares. But you will save on taxis to/from the airports.
3. You mention concern about fuel costs. They will be noticeably less than fuel charges for the equivalent distance here in Australia.
4. If you follow the itinerary I gave you, it is a quick dash over the hills from Half Moon Bay to San Francisco airport, if you want to drop the car off and not have the nuisance of the car in downtown San Francisco.
5. The itinerary I gave you would definitely require two full days. It is fairly boring from Las Vegas across to San Luis Obispo (where I suggest you stay overnight). The second day is far more interesting. Certainly visit the Hearst mansion at San Simeon (extravagant, spectacular, bizarre and over-the-top) and do the 17-mile drive at Carmel and take in Monterey, where the aquarium is excellent. Make sure you read some Steinbeck beforehand (eg Of Mice and Men, Cannery Row or Tortilla Flat, all set in the Monterey area.)
Cocitus 23