A nice route over the hills from Palo Alto is to just head straight up Page Mill Road. When you get to Skyline Drive, just go straight across. That's called Alpine Rd. Then turn left when that ends at Pescadero Creek Rd. That will take you to Pescadero Beach. If you don't particularly care about whether you end up specifically in Half Moon Bay, but just want to get to the beach, that's a good route. If you want to go to Half Moon Bay, you would have to head up Highway 1 15 miles.
Not that big of a cyclist, but I have driven the route and traffic is low. I did hike from San Carlos to Half Moon Bay once, in a day, so you should be able to bike both ways in a day.