If you want to fish on a head boat keep in mind that most of them don't start sailing for tuna until September, although a few may start in late August. If this is not an issue there are many good choices out there with the Voyager, the Jamaica, and the Doris Mae a few of the better ones I have fished and liked. That said, there are many other good ones you'll likely hear about on this board.
If you want to fish in the summer and sleep on the way out, there are also a number of private charter options that are also exceptional. In addition, a private charter will give you the opportunity to both troll and chunk, which in many scenarios can greatly increase your odds of catching. If you do choose the private charter option Mark Deblasio on the Canyon Runner is an exceptional choice worth pursuing based on first hand experience. I'm sure the Pez Machine, Fish N' Chips and Warden Pass will also put you on fish based on the strong reviews of these boats frequently posted on this site.
Best of luck and let us know how you do when in fact you do get out