Karen’s place is a nice stay for a weekend getaway - everything you need is within walking distance of OB. You can even take the bus 923 to and from the airport. Getting to Mission Beach, Pacific Beach, La Jolla, Convention Center, all the major attractions etc etc is accessible by bus or trolley but it does take 30 mins - 1 hr as a lot of transfers happen in Old Town. If you're short on time, rent a car while at the airport. While in OB, try Plant Power Fast Food and Roberto's Taco Shop for big portions after a day at the beach. And give Molly a few tummy rubs and scritches, she is a very good girl.