I don't know about San Diego, but it was my experience in various locations across the country that Park-and-Fly rates are not typically loaded into the inventory that is available for online booking. You may need to contact the hotel directly to find out. Typically, Park-and-Fly rates are very attractive, especially so on weekdays. One trick I always use is to book the property first for a regular rate online (to get an online booking bonus), then call the hotel and ask them to change the rate to the Park-and-Fly one without changing the confirmation number.