The location is fabulous. Take a five minute walk to Oceanside Marina with its deep sea fishing boats, sightseeing boats, Catalina Island or whale watching boats in season, not to mention the great seafood restaurants, coffee shops, and specialty shops. Or rent a water raft or boat. Or go the other way, ten minutes south to the pier and fish if you like or watch the fishermen or walk to the end of the long pier and have something to eat in the 50's style restaurant. Many restaurants of all types are located throughout the area, on or near the coast. Enjoy a martini by the water or have a great seafood, or other dinner.
You may want to visit some of the many attractions in the area. Legoland is down the highway about 20 minutes. Wild Animal Park is inland about 40 minutes. Seaworld is south about 45 minutes as is the San Diego Zoo. Disneyland is north about one hour. Downtown San Diego is about 50 minutes south with access to Coronado Island nearby. Or visit the Gas Lamp District for food or fun. Del Mar Racetrack is about 30 minutes south. Many other attractions abound in the area. Of course, all times are approximate. The Old Town Trolley will take you to many places in San Diego. Take a pleasant modern train ride from the Oceanside Amtrak station, a five minute ride or 20 minute walk fromn your unit, and you can be in San Diego in an hour or so or attend an Angel ball game or go to Disneyland.
You may want to visit Tijuana. Enjoy your choice of activity.