The reefs around Negril are supposed to be better than Ocho Rios.
I've been to both Ocho Rios, Montego bay, and Negril, but have only dove in Negril. I went thinking the diving wouldn't be that good from all the stories I've heard. It actually wasn't that bad. I mean you can do better diving in other places and If I was going on a "dive only" vacation I'd choose somewhere else, but for going on a nice relaxing vacation with the non diving spouse, I was happy with this.
One thing though about "Jamacia resort diving" is they do resort diver entry level diving. This is ok with some, but some people want more advanced dives. They also tend to do many of their dives as single tank trips. Just check before you go and see what they have to offer.
The water in Negril was crystal clear. You could stand on the boat and see the bottom at 100feet like it was only 20 feet deep. Some of the best vis I've ever dove. Even compared to Bahamas, Aruba, etc. The coral was good, but not perfect. Fish life was existant, but not abundant (due to some overfishing).
The water in Ocho Rios was so murky that if you waded in from the beach up to your chest you couldn't see your feet. Needless to say we didn't dive there.
As for rudeness and pushy vendors, this all depends on the resort area. Some resorts there the workers are great. Others are lazy. All the vendors are pushy somewhat. I found the ones when leaving the Dunns River Falls area to be the worst we encountered though. Simple rule is to ignore them and avoid eye contact. If you make eye contact with them then they will try to "reel you in". If you give them cold treatment they go on to the next "sucker" tourist and not bother with you.
-mike