hmmm, we have similar stuff that happens here, but basically I find you choose the ride you want / need to do. If that means doing the ride where you hang on as long as possible and maybe get dropped, so be it. If you want a group to stick together, then do the rides that have that.

Irulan's suggestion sounds good - depending on what your own goals are and whether the suggestion fits in.

It's nice to keep a look out for other riders, and as a Level 1 coach and knowing what it was like for me to start out riding, I'm all for encouragement etc. But not if it's going to cost me my own goals. I find I'll hook up with newer / recreational / slower riders on my recovery days, where my pace is suitable for them, and it works all round.