I went on Franks tour in October we did the City/Colonial tour. I was extremly impressed with Frank who answered all my emails and questions promptly, loves his country, and was very knowledgeable and fun. He took us to Ricks cafe in Mazatlan. It was beautiful right on the beach open air and had excellent food. I did not get sick nor did any of the 12 women in my group. I tried Blowfish for the first time and it was very good.
Note- (You can take Pepto Bismol before eating to coat your stomach and kill any bacteria if you want to be on the safe side. You can also get a prescription for Ciprofaxen to take with just in case) but I even forgot to say no ice in my drinks and I was fine.
Honestly I worried as well but Frank reassured me no one has ever reported getting sick at any of the places he brings people to. He did a wonderful job, we got to see so much more then the ships offered and he did a custom tour for us. I highly reccomend him!