Google Maps does not show the bicycle path along Trabuco Creek, which runs to the coast, as a street.
Begin on the San Juan Capistrano Amtrak/Metrolink station platform. Walk south to Verdugo Street (closed to motor traffic) and cross the tracks to reach Los Rios Street. (Google Maps does not show the connection, but there is a pedestrian crossing.) Turn right and go north on Los Rios Street. At Ramos Street, turn left (west) and continue until you reach the bicycle path at the east bank of Trabuco Creek.
Turn left to head south on the path, which continues along the creek, passing under Del Obispo Street. Just north of the junction with San Juan Creek, use the bridge to cross the channel and continue southwest on the path. (Vivente de Marlita and other streets parallel the path for short distances, but they are each separate roadways.) Ride under the bridges at Stonehill Drive, State Route 1, and Pacific Coast Highway/Beach Road.
In Doheny Beach State Park, leave the bicycle path to go southeast on your choice of Beach Road or the Pacific Coast Highway. Either route can be navigated by bicycle; they will eventually join together to go south towards San Clemente.
Finally, if you are planning to return by train, beware. Solana Beach is the rail station serving the Del Mar race track (season ending September 3). The patrons of the turf returning to points north are numerous and not noted for their civility, and some of the trains may be standing-room-only, especially on the weekends. (On Amtrak, a business class reservation will assure you a seat, but there are no bicycle hooks in the business class cars.)
You may also want to refer to the following: