As you're riding the Estero
trail you'll come to a large cattle pen with some feeding troughs and a water silo. There are a mess of cattle tracks leading everywhere, but just look for the sign pointing due south towards Drakes Bay with a fairly well defined trail behind it.
This is your route - follow it out as it takes a straight shot out towards the shore. The trail angles slightly downhill until just near the end where there's a small climb followed by a steep downhill before topping out above the cliffs overlooking the bay below.