Jamaica is very hot and muggy in August...... You'll want to change clothes several times a day! Also be aware that the annual Reggae Sunsplash festival is generally the first week of August (or the last week of July); this event brings in about 75,000 tourists to Jamaica's north coast so Montego Bay, Negril, & Ocho Rios tourist facilities get a bit taxed and every street hoodlum appears.
If staying at an all-inclusive spot like Sandals this may not be a concern. Lots of folks go to these places and, once there, never leave to see the "real country" that they are visiting. If that's what you want, you'll enjoy yourselves a great deal.
