Im sharing a point of what an American could expect going down there.
I think both our points are valid, but you are setting American brothers on here up for a bad time if you tell them "Its fine" to be walking around talking on their phone. Especially when a new Galaxy or Iphone that even down there is sometimes multiple times the monthly salary of even Brown people. I was identified as a foreigner immediately walking into places long before I would open my mouth. Folks there know.
Respectfully, So what if you are a foreigner? Talking on an iphone? (they are useless stolen and also trackable) What you describe people do it all day every day. local and foreigners alike. FYI Jamaicans residing overseas who visit are also "foreigners"
Time and place matters. I think the whole "Walking around" concept is throwing me off. What are you doing? sightseeing? Where?
I would recommend to anyone to know what they want to do, then make arrangements and not wander aimlessly.. take uber, hire a driver etc.
The whitest europeans with their backpacks have been to places I have never seen and the chinese and europeans are in the ghettos having the time of their life.
Stop acting scary man and get informed / be prepared on your travels. Feel free to ask me for travel advice as well. Jamaicans have nothing against black people from America or otherwise.