In live in So Cal so I seldom if ever, do a ride without seeing another cyclist or mountain bikers. I find both groups to be equally friendly however, maybe 'cause its California they are more subtle. Typically I don't get a wave and a "HI!" I get a head nod or a finger lifted, some acknowledgment, however slight, as we pass on the road or trail. More often than not a mountain biker will be more vocal but I think that's because of the trail - if narrow singletrack, if that biker wants to get around this old, slow pokey person, he better be letting me know so I can pull over and let him pass by or if we are coming in opposite directions, its good to communicate intentions.

Usually if I'm ignored it is on the road but I don't attribute that to rudeness. When I chugging down the road, I'm thinking zen thoughts about my cadence and my breathing and my heart rate and by the time I notice another cyclist, we pass too quickly by (cause I'm usually faster on road than trail) and it's too late to say or do something. No problems, I just keep chugging.