As far as I know "OH DANNYBOY TOURS" has been there maybe a year. Not saying anything bad about them, but your best bet is to book through your hotel to get tours that will then be backed up by your hotel, as Pedro1 mentioned above. If there is a problem, which are rare, the hotel and the tour company will see to it that it is remedied. Some hotels even rebate any savings back to you.
Example. A guest of ours found a "divemaster" who would take him out diving for $10 less than the local dive shops. He booked it himself. After the "guide" picked him up and got him out on the water, he informed the guest that he would also have to put gas in his boat. When the dive started, the equipment was faulty.
Needless to say, he booked the rest of his dives through our Inn. I'll say it again, in San Pedro, just like anywhere else in the world you generally get what you pay for.