There are many interesting musuems in Balboa Park and they vary according to themes. Most museums focus on history and the arts, while others feature sports and science. If museums are your thing, then this place is definitely for you. And aside from the museums, the architectures and the gardens are just so beautiful!! If you want to learn more about the park, read this:

Balboa Park: A place of culture and leisure

And if you're planning to visit San Diego, make sure to explore the rest of their site as it is very helpful:

San Diego Hotel Reservations

San Diego Hotel Reservations Guide