I also prefer   lots of privacy,  but when I am going around the town,  

I will often speak with strangers. 

   When in a store, I note very carefully which people going down an aisle makes eye  contact and who doesn't, and who smiles  (which means I smle back).

    Sometimes the people around in public life will not smile at all, whereas other will and will also speak with you.  The nice people of the world are the ones I want to know.

I don't like chatting with strangers. But My Grandmother and Mother always talk with strangers. At the end of trip, they have a lot of telephone numbers. I admire the old people.

Here in France people are more welcoming and they do help you guide if your looking for some place or some informations. 

I have made few friends in bus stops and tramway here.. most often I'll start the conversation because sometimes there might be some small strikes or some technical problems for the bus transport so I'll ask them if they're aware of that... and that's how conversation begins... 

Sometimes I ask people for some informations it may be about the nearest post office, supermarket, etc.. Voilà....

Some people don't come close to strangers because they think it's dangerous, to talk to strangers, but in my country it's very normal that you can have a conversation with people, on a train, a bus, a plane, because people are very friendly here. You can get to make friends with a smile, don't be afraid to get close to someone if you give confidence, for me it's very pleasant communicate with peoople anywhere.

I don't have a problem talking with strangers, (or at all actually!), but it depends a great deal on the situation.  There are several factors affecting whether I will talk or not.

First, as many have mentioned, I have to feel safe.  

Second, if I'm on a bus, train, etc., I don't talk because I don't want to spend the next 4 hours or however long talking about someone's health issues, etc.

Third, I have to be "in the mood".  Sometimes I just don't want to talk.

If I feel safe, I'm not on public transportation, and I'm in the mood, I can talk to anyone about anything!  In fact, my children complain that I know someone in every store we go to and that I waste time talking to all of them!  I love a great conversation and have no problem starting one!  I do feel really tired after a long day of being with people, however.  I think I'm either an extroverted introvert or an introverted extrovert :)