I did my open water scuba certification through Saguaro Scuba and I couldn't be happier that I did. I got a good deal on Groupon, so check there in case they're still offering it.
The shop itself has everything you could ever need. And if they're out of your size, just let them know and they'll have it ordered asap.
I bought all of my gear from there - great quality. And I absolutely have to give a shoutout to my dive instructors, Amber & Tony. If you're taking a class there - request them. They were simply the best. Great mix of humor with a wealth of knowledge.