I went on a cruise last year with HAL. I did dives in Cabo and PV as well. I dove with Lands End Divers in Cabo (
http://www.mexonline.com/landsend.htm). Everyone at there shop was very friendly and helpful. They split the divers up by experience, which was nice. Our DM was "Chucky", again very friendly and helpful. We dove Pelican Rock, which was my first dive after certification. No current, no swell, and about 50-75 foot viz. It was a wonderful dive full of lots of fish of all sorts. All in all I had a wonderful time with them. My only regret was that I only got to do one dive that day because HAL didn't offer a two tank dive. If you have a one tank signed up through the ship I would suggest asking whoever you dive with to go on a second dive after your first. The dive sights seem to be no more then 10 minutes from the harbor, and boats they used were a bigger water taxi with a canopy. My only VERY small complaint was that we had to walk quite a ways to and from the shop to get the gear and then onto their boat.
PV was a little different. I dove with Vallarta Adventures (
http://www.vallarta-adventures.com), again booked through HAL, but this time for 2 tanks. It is a LONG boat ride to our site, Las Marietas. It was also a cattle boat with about 50 snorkelers from 2 cruise ships and about 15 divers. I have to say though the staff was really great at telling jokes and stories on the way out which helped to pass the time. It was like going to a comedy club. We even stopped to do a little whale watching. They split us up by experience so each DM had 6 or 7 divers with him. I forget the name of my DM, but he was skinny and bald, if that helps. Anyway, there was a bit of a swell at our dive sites so some people got seasick, especially after the long boat ride. There were no where near as many fish, and the reef looked pretty dull. We did get to swim through some lava tubes, which was fun. But after the two dives we had another long boat ride, this time in a water taxi, to catch up to the main boat where the snorklers were. In such a small boat and in high surf for what seemed like 30 minutes I got a little sea sick. Then it was another long trip back and by then I felt terrible.
To sum up, both dive operators were good, but Vallarta Adventures really packed their boats. If I had to choose I would have done 2 tanks in Cabo and done something else in PV.
Hope this helps and have fun!