Totally agree with BarDar. Do your classroom and pool sessions at home as you don't want to be studying when on vacation. Then just bring done your referral papers and do the 4 open water dives to get certified.
As someone who is brand new to diving; I would suggest NOT buying any expensive gear until you know you like it. BUT I would go ahead and buy your mask, snorkel & fins. A good mask can make your experience so much better whereas a poor fitting mask can ruin the whole dive. It is also good to have your own fins that you know fit well.
Even if you don't like scuba diving...you will have your mask, snorkel & fins for snorkelling for many more years to come.
Diving since 1987
Couples Negril - September 2011, 2012, 2013 and have just booked 2014
Scuba Club Cozumel - Jan, Apr & Nov 2012 and Jan & Nov 2013
Cobalt Coast, Grand Cayman - May 2013
Retiring & moving to Cozumel, Mexico in early 2014