There are various things close to various conference sites - where is the conference held? You've already gotten lucky. San Diego is the greenest and prettiest I've ever
seen it and the back country is even pretty and blooming. The desert blooms are at "gorgeous" and headed for "spectacular". Anza Borrego state park has good trails, rental car company or hotel can fix you up with a map.
We have seal pups at the Children's Pool in La Jolla, to the annoyance of some of the natives. Children have not been able to use that cove for several years now due to the harbor seals and the sea lions. The rest of the shoreline around La Jolla, with parks and whatnot, will soak up the rest of a day.
I like the Animal Park but that's an allday excursion and your wife would like to go along, I'm sure. The animals are separated by continents, more or less, and left as mixed populations in these huge enclosures (carnivores are separately caged.) There's an electric train that the people ride around to view them, with the result that the humans are caged and the other animals are running around loose. Very good breeding success, too - it's spring so you'll see babies.
Downtown has the Gaslamp Quarter, which is interesting but distinctly touristy. Lots of places to eat, listen to music. Balboa park is definitely worth roaming around - their link is Balboa Park
and has a schedule and maps. The Reuben H. Fleet Space Museum (in Balboa Park) is good for half a day, all by itself. And has a kick-a$$ giftshop. With lots of science toys.
If you feel like roaming the backcountry, a map and a rental car with that GPS "neverlost" system is the way to go. Try the country around Julian. Or Alpine. That's about the best we can do for mountains and, if you've ever seen the Rockies, they're very modest hills. There may be a deer. Or a possum. Skunks are common. Palomar has the observatory, I don't know a thing about tours inside the thing but it's a good long scenic drive up and back.
How many weeks did you say that conference was? I think I've gotten carried away!