It's touristy but some of the restaurants behind the hotel, on the walk along the water, are fun. It might be interesting to eat in the US Grant (Starwood Luxury Collection iconic historic hotel) and one of the trendy boutique hotels (sorry, I don't remember the name) has a good foodie place. If you walk to the GasLamp district (basically the part of downtown with some district buildings), you'll find a lot of restaurants and bars.

With a car, it's fun to go to LaJolla village.

I haven't been there in a while, but there's a restaurant near downtown LaJolla, along the sea in the direction of the UCSD campus, that's built so that it seems to hang over the rocks along the coast. I think of it as a fish place, but it has a variety of choices, vaguely American/Continental food. It's especially interesting to go here during a storm and get the waves crashing into the thick windows at your table. Very dramatic, but it might seem scary to some people.