Only have three days in San Diego? Here is a route that covers the highlights without feeling rushed.
Day 1: Downtown & the Harbor
Start at the USS Midway Museum, walk the harbor to Seaport Village, then spend the evening in the Gaslamp Quarter for dinner.
Day 2: Balboa Park & Old Town
Spend the morning at Balboa Park and the San Diego Zoo, then head to Old Town in the afternoon for historic sites and an early Mexican dinner.
Day 3: The Coast
Spend the day in La Jolla, starting at the Cove to see the sea lions, then work your way down to Sunset Cliffs for the evening. If time allows, add a whale watching or harbor cruise in the morning before heading to the coast.