I went on an 8 day trip in early June last year aboard the Islander. It was a great trip but that time of year you won't need the real heavy gear.
You will spend a day in the albacore grounds between 100-120 miles out of San Diego then head down to Guadalupe Island for Yellowfin (probably not, too early) or San Benitos Island for a day or two of very LARGE yellowtail action. You will then head towards Cedros Island for yellowtail action again and make another stop in the albacore grounds on the way back to San Diego.
I had the expectation of catching larger fish and more species of fish on the trip, but found out that this is just too early in the season to expect much else then albacore and yellowtail. Don't get me wrong, it was a lot of fun, just nothing that would take more than 40lb. line.
If your goal is to catch larger yellowfin, bluefin, wahoo etc. then plan on a 10 day trip in October or November.