Yeah - sorry to tell you this, but on mixed use trails pedestrians have the right of way. Yes they should be aware they are sharing the trail, they should not block the trail by walking many abreast, they need to be aware of traffic and not recklessly step out and such and I know how frustrating it can be when the walkers are ill behaved and rude, but you as a cyclist have the responsibility of always being in control also. If you feel as if you are constantly in danger of hitting someone at the speed you are traveling, chances are you are traveling too fast (though somehow I suspect you are exaggerating a wee bit about the 30mph bit....), passing too close etc. Just think of yourself as the car and the peds as you on your bike. You want respect and safe driving from the cars when they are near you? Well, the pedestrians have the right to expect the same from you as you are the bigger, heavier and faster individual in this case.