My 2 cents:
-Definitely buddy up with someone, even if you're in a "group"; talk over a dive plan with your buddy, and dive it.
-Let the others in your group know what you're doing, "hey guys, so-and-so and I'll be buddied up - we'll tag along for a while and might split off - if we end up separated from you guys, we'll meet and be at the float until xx:xx and on-shore after that..." - you get the idea. This seems obvious, but goes a long way to avoid confusion when you & buddy or the others surface and wonder what's next...
-Doing the above can actually begin to set an example for the rest of the group - heck, they may even get the same idea to buddy-up, too
-After buddying up, making a plan and, of course, BWARF'ing
, don't worry too much about the rest of the group or how they're diving. I started out vacation diving on cattle boats, and if I worried about how safe or capable everyone was then, I'd have worried myself right out of the water (it's a wonder I became a DM!).
-After being safe, most of all enjoy the diving and the people you're with. If you don't like the people, find people you like - plenty of 'em out there, trust me!