The San Diego Cruise Port Terminal is basically in downtown San Diego. There are close hotels and restaurants, within walking distance.
Starting or Ending in San Diego
The San Diego Cruise Port Terminal is very close to the San Diego Airport. There is no need to pay much to get to the Cruise Terminal. If you are up for it, it's possible to walk. It's about a 2 mile walk but the weather is usually nice and the views are of the bay as you walk.
A taxi is fast and cheap since the distance is so short.