When to say " hello"

When I walk at the seashore I often encounter other walkers, strollers and bench sitters. At each encounter I have to decide whether to say "hello" or not. It is an interesting judging game I play. If their is more than one person, and they are talking to each other I usually don't say anything. They are engrossed in each others company. Most are happy to say hello back, sometimes offering some other comments like "beautiful day." Some are running... its hard to talk when your running. The people walking dogs usually let you admire their pet and often tell you a bit about it if you ask. Occasionally people don't want to connect; they have come to the beach to think, or cheer them selves up or are just too engrossed in walking. ipods often prevent communication.
Some stop and have whole conversations with you. Several days ago I stopped to ask someone about the new construction going on at the beach. A new building was being built. She knew what the building was going to be and I was grateful for the information. A new visitor's center; its been planned for sometime and just now is going up. One time I met an older man who when we exchanged greetings gave me a small christmas tree, it was that time of the year, he'd made out of wood. He was giving them out. Hard to refuse a present.