There's more snorkeling than diving at Cabo Pulmo, if the shops on the beach are any indication. The reefs are shallow and lovely, and quite worth snorkeling or diving.
Keep in mind that Cabo Pulmo is about an hour and a half by car from the more industrialized San Jose del Cabo (where the airport is), and two hours from the ultra touristy Cabo San Lucas. Cabo Pulmo is a tiny place, with not a whole lot going on other than the beaches (which are lovely), some hostels, and a handful of beachfront diving/snorkeling operations. There are some good restaurants within easy walking distance as well. The last several miles into Cabo Pulmo are by dirt road ... the nearest town, La Ribera, is about a half-hour away by car. Once you're down there, unless you have a car there's not much to do or see other than what you can get to from the beach. Might not be enough to keep you busy for a week.
Another option would be La Paz ... roughly 100 miles north of Cabo Pulmo. It's a much larger town, with lots to do and see. The diving's amazing ... and we had some snorkelers on our boat the day we went out to the sea lion rookery. On our second dive, which was a wreck, we dropped the snorkelers off on a nearby beach, and they were later raving about how good it was. So that's another option to consider. Also, there are direct flights into La Paz ... so you can avoid the more crowded and expensive Cabo area altogether if you want to.
Loreto's another 230 miles or so north of La Paz. It's much smaller than La Paz, more temperate (this time of year, not as hot), with mountains looming in the background that come all the way to the water. Loreto was my favorite place, but there's much less to do there than in La Paz. You can also get direct flights into Loreto, via Los Angeles. The water here was quite chilly (we were wearing 7 mm wetsuits), but there were snorkelers on our boat and they had a delightful time. This is where we were surrounded by dolphins, and on the way back from diving the driver spent some time looking around for a whale shark (although we didn't find one) ...
... Bob (Grateful Diver)
Threats and ultimatums are never the best answer. Public humiliation via Photoshop is always better - airsix
Come visit me at http://www.nwgratefuldiver.com/