I live about 20 min from Laguna Beach. More than likely you will think it is warmer than we do. Anything below 70 degrees and we break out sweaters and Ugg boots. The highs should be in the mid to upper 60’s. Walks on the beach will definitely be possible (as long as it isn’t raining) just not in a bathing suit. I recommend Crystal Cove State Park (just up the road from Laguna), if you go,have lunch at Bear Flag Fish Co, at the Crystal Cove Promenade, also 1000 Steps Beach (in Laguna), downtown Laguna Beach. if you like to walk my favorite walk is Balboa Island in Newport Beach, there is a boardwalk all around. You can take the Ferry across to Balboa Peninsula, and be sure to have a Balboa Bar.
For clothes I would say layers but during the day you will be fine with light paints and a light sweater. It is an El Niño year, but so far we have only had a couple days of rain.