San Diego's walkable neighborhoods include Hillcrest, North Park, Little Italy, the Gaslamp Quarter, and parts of Pacific Beach and Ocean Beach. The MTS Trolley covers downtown and key corridors but most San Diegans drive for most trips.
Hillcrest, North Park, South Park, Little Italy, the Gaslamp Quarter, downtown, and parts of Pacific Beach and Ocean Beach. University Heights and Normal Heights are also walkable.
The Trolley has 4 lines (Blue, Orange, Green, Silver) connecting downtown, Mission Valley, La Mesa, El Cajon, and the border. It's most useful for downtown commuters or trips between served neighborhoods.
Downtown itself, Little Italy, Bankers Hill, Hillcrest, or Golden Hill all put you within a 15-20 minute commute to downtown jobs by foot, bike, or Trolley.