You'll enjoy diving Boynton Beach. I think they have some of the nicest reef dives in Florida. You will be doing primarily drift diving over the reefs, which are the most relaxing type of dives to do becuase you don't have to worry about working your way back to an anchored boat!
To answer your questions:
I usually dive with Loggerhead Charters out of Boynton Beach (
http://www.loggerheadcharters.com/). I'm sure NetDoc will chime in and second the recommendation for them. I haven't had to rent any equipment except tanks in Boynton, but John and Jim at Loggerhead have all the rental equipment you could need. Just let them know in advance to have it ready for you.
Another dive operation out of Boynton I have used is Dive Charters International (
http://www.deeper-dci.com/). My luck with them hasn't been as good. In my experience, they consistently leave the dock late, and they have actually bumped me from an underbooked boat. Leaving the dock an hour late wouldn't be a big deal for you if you're staying in Boynton (I have a 2.5+ hour drive home), but having a dive trip cancelled can ruin your day. However, their boats are spacious and speedy, and their DMs are good. I believe they can arrange for rental gear as well.
One note about DMs. Neither of the dive operations I mentioned above puts a DM in the water with you. That means that someone in your dive group (not necessarily you or your girlfriend if you are placed with a larger group) will have to carry the rope to the flag. It isn't a really big deal, but I have seen new OW divers surprised when they weren't offered an underwater guide.
You probably won't need your 7mm suits unless you're coming down in February (and even then I get a lot of good-natured hassle from the hardier divers about my 7/5mm and hood in 70 degree water!). Your post didn't mention when your trip will be. The water right now is running 82-84 at 60 feet. In October, the tempatures will drop to the upper 70s. Mid 70s by December, down to about 70 in February.
While you'll want to bring your own mask, fins and snorkel as well as your BC and regulator if you have them, you may want to consider renting wetsuits if you don't want to invest in something lightweight for warmer water diving.
Let us know when you'll be down. We make the drive to Boynton about once a month to dive, maybe we can bump into you!
Julie