Yes, cruise ships certainly represent homeless populations: close quarters, eating at tables serving eight at a time, an affluent clientele that can afford health insurance as readily as a multi-thousand dollar vacation.
The nursing home in Washington State that served as a covid-19 hot spot was not a homeless encampment. It was a nursing home with medical staff on hand.
I am not concerned about isolated homeless encampments as a major factor in the spread of the disease. They perhaps epitomize self quarantine and do not interact to a significant extent with others at the movies or the mall or large social events.
Seriously, when is the last time you've been within four feet of a homeless person?
So far, the majority of infected people who've spread it to other countries have been people on vacations or attending professional conferences in other countries who then brought it back and infected others amongst their families, colleagues, or casual acquaintances.