As the crow flies I am about 10 miles from SAN. Im out in Chula Vista if you know where that it is.
Looking at a map of the SD area, it seems to me that you would get excellent reception with an outdoor antenna or even a higher quality indoor antenna (handheld upgraded antenna). There do not appear to be any hills higher than you or the SD airport in between you both, which means you probably have excellent line of sight between you and ATC's transmitters. (My father used to live right on the beach at Mission Beach, so SD became a second home for me back in the 80s.)
I live about 15 miles or so from my airport and there are a couple of higher ridges between the airport and my house. The standard antenna worked marginally, but when I mounted an outdoor antenna reception was excellent. This was an important factor in my decision to provide the feed to LiveATC.