Del Mar Aquatics used to be on of the top notch dive ops on the island, I don't have any personal experience with them but now-a-days they seem to cater more to the cruise ship crowd, not that that's bad, it just means that they are more of a 'cattle boat' style dive op, using larger boats and having a lot of people on them. I don't know much about thier safety record or DM's, this is just an observation as I stay at a hotel right next to thier pier and see the coming and goings of the operation.
These days the top 3 recommendations I have for dive ops are:
1.) Dive with Martin, the dive op I've been personally using for the past few years, good DM's and captians, well maintained boats 6-8 divers max per boat, usually 2 dm's if the # is above 6 and some of the best prices on the island with free videos and night dives with multiple bookings. he is also collecting used prescription glasses and hearing aids for his charity and will give a discount or free night dive with a donation. visit the website for more info
www.divewithmartin.com
2.) Blue XT Sea Divers, Christi has built a very fine dive operation in just a few short years, everyone that has used her services raves about the DM's, captians and services.
www.bluextseadivers.com
3.) Bottom Time Divers, Raul Plates was my DM when I used to dive with Blue Bubble Divers, he has gone out on his own and is starting to build his business. He is a wonderful DM, VERY safety minded and really good at finding critters.
www.bottomtimedivers.net
all these folks will give you much more personal attention than a service that has large boats with lots of people on them.
hope this helps, happy diving!!