Is Divemaster Gilbert an instructor as well as a dive master?
My personal position on getting certified is to do it at home before you come. That way, you don't have to dedicate any valuable vacation time to study, and already being certified, you will be able to dive and enjoy.
In the absence of complete certification at home, I agree with sandb. Do your classroom and pool work at home and get a referral from your home shop for the open water portion.
Whether you decide to go through with your complete course or just do the referral in San Pedro, what is most important is the instructor. You need to make sure that not only is the instructor well qualified, but also that you can relate to the instructor's communication style.
Upon your arrival, meet and have a long talk with the instructors you've decded to consider. Have some questions prepared and see how they are answered. Further, trust in your gut reaction to the instructor. If you like the answers to the questions and you like the way those answers were expressed and you like the person, then it is probably a good match.
There's another reason that I don't recommend complete certification while away on vacation. Believe it or not, not everyone that wants to get certified actually enjoys the experience, some can't clear their ears, some find themselves claustrophobic and a myriad of other reasons. Should this turn out to be the case, you are better off to find that out in the pool at home, than after committing to certification at your vacation destination.