The why could be very important.
Folks here do not take kindly to being photographed at the moment. Well, you would be a bit camera shy too if your house fell down and you only had 2 changes of clothing and nowhere to shower!
They are more than a bit sick of it - only today driving past a collapsed house, my colleague took a photo for his wife and got shouted at - people are becoming more sensitive.
You will probably have to explain yourself and the reasons had better be good.
And to be honest, most of the places where you will find what you describe are not places you would want to go without a proper plan.
Unless of course you are or appear to be Haitian.
I am not just trying to pjss on your chips here - what I say is true.
If you still go ahead then from Sosua you can get the CaribeTours bus to Santiago early in the morning and then another CaribeTours from Santiago to Cap Haitian.You will arrive just in time or a little bit too late to take the Tortugair or Caribintair crop-duster down to Port au Prince (US$85 - one way). If you miss it in the afternoon then there is one early in the morning. Fun can be had in Cap Haitian.
From the airport in Port au Prince - just follow the stink but be careful!!
The alternative is to fly from Santo Domingo SDQ with American Eagle departing at 8:35am.
That goes straight to PaP and costs around US$350 for the 45 minute flight.(rip off gits!!!)
Hotels in Port au Prince are about twice the price of Santo Domingo for less quality and comfort. They are pretty booked up most of the time these days with people like yourself. Official taxis are non-existant. You can find someone to drive you for the day but be careful about getting in a stranger's car in Port au Prince.
Downtown you will find the collapsed houses and uncleared rubble. The road out to Carrefour and Leogane has everybody's favourite camp to shake their head and tut at - the one in the median in the center of the main road.
Be careful - and let us know how you get on.