Re: San Diego
All the San Diego Bay charters are off Shelter Island, which is a quick 2 or 3 mile cab ride up Harbor Drive from the Convention Center.
I am partial to H&M Landing, but truthfully for a 1/2 or 3/4 day, they are all the same. When looking up charters or rentals, make sure they are on San Diego Bay, not Mission Bay, those are different Bays
As was earlier mentioned, right now--around May to July--is, unfortunately, as close as we get around here to a "slow season" as regards fishing. Spring spawn is over, and Fall spawn is some time off. And Yellowtail are much more likely the closer you get to August/September.
1/2-day trip will go maybe 2-3 miles out, around the kelp beds. Those are going to be quite slow right now unless--as was also mentioned--YT are in close; and that's a
serious crapshoot right now.
As the captain is going to spend a lot of time chasing around for fish this time of year, I would strongly suggest a 3/4-day trip to the Coronado Islands (Mexican waters). It will cost you more, but you will get much more fishing time and be more likely to find something to catch, whether that be calico, sand bass, or YT.