It takes 3.5 hours from LAX to San Luis Obispo (101), and another 3 hours from San Luis Obispo to Monterey by HWY 1 although it is only 130 Miles because in some area (close to Big Sur) the speed limite is only 15 miles.
You need spend another 1 or 2 hours, at least to stop at Julia Pfeiffer Burns State Park, walk along the coast.