It is beautiful. The route There are any number of starting points. To avoid the most traffic, come south on Silver Strand. Just past the high-rise condos on the ocean side you'll find a small public parking lot. You can start here.
Tip sheet Make a real adventure of it.
Take the ferry from downtown San Diego. You can take the bay trail under the Coronado Bridge, along the golf course and around Glorietta Bay. This will add two miles each way. Stay on the ocean side and you'll quickly pick up the protected asphalt trail that runs all the way to Imperial Beach. On the inland side is the San Diego Bay.