Hi Another Linda,
First: We too walk the exec courses. Although we are not there during snowbird season, we usually see many more walkers than riders on the exec courses when we are there. If someone grouses about you walking, perhaps you might say cheerfully, "Don't worry. We play ready golf and are conscientious to keep up with the group ahead." That might ease their troubled mind-- and even preempt your second concern (although people often don't see themselves as part of the problem).
Second: Without directly pointing out someone else's lack of golf etiquette, I sometimes will say something inclusive such as, "Oh, we are getting a hole behind. Let's pick up our pace." If someone is just sitting in their cart until they can hit, perhaps ask, "What club do you use from this distance?"
Might work. Might not.