Just back from 2 wks in Cabo. Did a day trip up to Cabo Pulmo, was disappointed. We hit a poor day (visibility poor, current high, etc.). I hear that later in the summer, the vis is more reliable. Had much better diving in Cabo itself...
Anyway, we went with Mario & his son (Cabo Pulmo Divers, I think). It's the outfit closest to the beach. They only take cash. The only outfitter in Cabo Pulmo who has a credit card machine is Cabo Pulmo Dive Center (I think) in Cabo Pulmo Beach Resort (2 story green building, you can't miss that). Everyone else is cash or travelers cheques. I did two boat dives w/ Roger of Cabo Pulmo Divers (pretty sure, Mario's outfit); first was the Vencedor wreck (tune up for the group), second was Los Meros reef drift dive. Big groupers & tuna, but no mantas/sharks at the time. Sea lions are supposedly fairly reliable if you go to the sea lion colony (I saw a sea lion at Pelican Rock in Cabo, but missed getting a picture).
The East Cape is much quieter than Cabo San Lucas, and much more economical than the tourist corridor. The sand in Cabo Pulmo is also very nice compared to Medano Beach in CSL or along the corridor. That said, if you're looking for 5-star accommodations, you won't find them on the East Cape
I'm working on a more complete report, & hope to post it within a couple of weeks. Meanwhile, check out my gallery for some shots (mostly Pelican Rock at Cabo).