There's about 400 miles of coast redwood from barely into Oregon all the way down to Big Sur. Do you have a specific place you plan to visit? The tallest trees are on the North Coast around Redwood National and State Parks. There are some pretty large groves around the Santa Cruz area. Muir Woods NM is popular because it's close to San Francisco, although it has relatively small trees in comparison to other areas.
A little more specificity and I'm sure people will be able to give better advice.