I am getting married July 4, 2016 in Jamaica at Secrets St. James. If you are still looking I highly recommend it we went there on vacation a few years back and loved the resort.
In regards to getting a room block I have already obtained one for my guests. They gave us a discounted rate, for every 9 rooms the 10th gets a complimentary upgrade, for every 5 rooms is booked the 6th is free (up to 3 rooms and this credit goes to you so you can choose to distribute throughout or keep for your self), and a $100 resort credit for every guest.
I went through Liberty Travel and they have 250 complimentary save the dates that are actually pretty cute unfortunately you can not add a picture though but it helped us save money. As I said we are almost 2 years out so you should not have a problem setting up the group rate. The only thing your guests will have to wait on in airfare because most airlines do not establish there schedules until 11 months prior.