There are three skimboarding beaches in San Diego, all within a few miles - The Wall (aka Wipeout Beach), Marine St. and Windansea.
Marine Street and Windansea are best in Summer, Fall, and Spring and offer straight waves and liners. The Wall is best during Winter, Fall, and Spring and has a sidewave as well as straight waves and liners. Big swells will usually wash away sand from all of the beaches, making the slope flat and causing the waves to break far out.
For most of the year a topsuit or springsuit is sufficient to stay warm. On the coldest days you may find yourself wanting a full suit. The picture on the right is of a liner at The Wall.