I learned how to scuba dive in the Sea of Cortez in San Carlos so I am partial to it. When living in Tucson, AZ, San Carlos was an easy weekend get away gut over all, the diving was ok.
My diving husband and I went to La Paz in August 2003 in hopes of seeing either hammerhead sharks or whale sharks and saw neither. The local divers told us that October is now the better month to see the large critters. This trip had been organized by our dive shop so we stayed in La Paz and used the Baja Fun operation. Staying in La Paz made the night light fun because there were plenty of restaurants and things to do for entertainment. The diving was good, plenty of moray eels, seals, mantas, scorpion fish but not too much in the way of coral. It was a fun trip because we met a great woman who is still a friend and we travel the world diving together.
The last place and the best place we've been diving in the Sea of Cortez was Loreto. When we went in July 2005, it was a sleppy little town popular with Californians for the deep sea fishing. The Mexican Government has been actively trying to develop the fishing towns along the pinnesula so I can't attest to it's current state, but when we were there it was very quaint and pleasant. Within the marine park, the diving was great! I had never seen such healthy corals in the Sea before. We had several pleasant drift dives and had a week of relaxing and enjoyable diving. Tons of scorpion fish and sargent majors. Usually saw 1 or 2 turtles each dive. But we never saw any of the big critters.
We always saw pilot whales when we were coming and going to the marine park. One day, we all jumped off with our scuba gear and the pilot whales just swam on buy us. It was a wonderful experience. One day we took a long boat ride to a pinneacle South of Loreto but North of La Paz (sorry the name escapes me) in hopes of seeing sharks but we primarily saw sea lions and each of us took turns pulling man of war tenticles off our necks. That being said, it was still a pristine dive. Being in the middleof no where with no other dive operations around can make just about any dive fun because you feel you are exploring it for the first time.
We stayed at the Baja Outpost in Loreto. The accommodations were basic, clean and with A/C. Meals were included and were delicious. The town is small and doesn't offer much in the way of night life, but sitting around in the hammocks, drinking cold beer and swapping dive stories with other divers was fine by us.
The Baja Outpost website made the resort/hotel seem more issolated than it really is. It is off the may street running along the coast. There is no beach or pool but if you want an experience other than main stream hotel, this iwas the place. The people there are nice and we enjoyed ourselves and the people we met there. The owner Leon from Brazil has lived there for years and has helped develope the dive industry there. He is an interesting man and very personable. A "little pie in the sky" dreamer yet has contributed a lot to Loreto.