Personally, I'm biased toward the Yosemite option. In the interest of time, you may wish to consider flying from San Diego to Oakland via a low-cost carrier like Southwest and drive to Yosemite via 580 & 120, to maximize your time in the park. As long as you don't attempt the drive during evening commute hours or mid-morning on a Saturday, your drive will be a quick and fairly painless one (although not very scenic). If you are interested in seeing both the coast and Yosemite, you may wish to consider flying from San Diego to San Jose and driving to Big Sur. Then driving from Big Sur to Yosemite via Monterey, as I think that will be both a great sampling of the coast while leaving you enough time in the park.