DH is attending a conference in La Jolla for 3 days at the end of May, and I'm going along. I'm looking for things to do to pass the time, and nice cheap/reasonably priced restaurants for lunch or a snack. I will have use of the car, but I would prefer not to drive very far from the hotel, the Estancia. I really don't want to go into San Diego as I have been there before and saw what I wanted to see there.

Birch Aquarium near Scripps is nice and low cost, not too large but good exhibits, we enjoyed it.

You might consider taking the very easy and leisurely drive up to Solana Beach and walk around Cedros Avenue
http://goo.gl/maps/CrrKc

http://www.cedrosavenue.com/

Drive to La Jolla Shores and have lunch. Maybe at Caroline's
http://goo.gl/maps/Qdjfv

Eat at George's on the Cove and go shopping.

Estancia is a lovely hotel, but you aren't really in walking distance of anything but the UCSD campus. You will need your car to get into La Jolla village. I stayed a the hotel a few years ago when my niece got married there.

go for a walk at torry pines state park. you could walk from the hotel to the torry pines glider port and have a picnic enjoying the view or walk down the cliff and enjoy black's beach. the home along la jolla farms road are beautiful. check with the university to see if there are any exhibits going on. pizza port in solana beach is really good. if you want a mall, university town center isn't too far. you say you don't want to go into san diego but pacific beach is a close easy drive on la jolla blvd and a nice place to walk with some cheap eats. on a clear day, take a picnic up to mt soledad.

I second the eat at George's on the rooftop - walk along prospect - go see the seals at the La Jolla "children's pool".... if you like to kayak go kayaking... it is wonderful. So great.