La Jolla is one of the most popular spots in San Diego and it is easy to see why. This part of the ocean is calmer or cleaner than other beaches, close to downtown and you can park not too far from a beach. Kayaking, diving, snorkeling, surfing, and paddle boarding are all popular, or you can just walk along the coast and watch the sea lions. Get there really early on the weekends and make a day of it. Avoid San Diego in May and June if you're vacationing, you risk showing up on a stretch of June gloom and not seeing the sun for a whole week.