If you cross the border with people who know the area and the language, your potential risks drop big time. Of course, you have to take precautions as you would travelling to any third-world country, however, things in Cap are much more quiet in comparison to the capital, Port-au-Prince.
There are lodging options outside of the city of Cap that would take you to some of the most beautiful beaches that the Caribbean has to offer. Cormier Plage is a lovely place to visit...nice rooms, tasty and safe food/drinks, and plenty of gorgeous beach, English speaking owners as well. There is also Labadee, the private beach area where the cruise ships stop. You can purchase a day-pass to enter and visit the sites and shops there.
Of course, the Citadelle and the Cathedral in Cap are worth seeing and could be done so within 1 to 2 days, that is really all you need in the city itself. It's the beaches that make the trip across the border worthwhile. They are, by far, some of the most beautiful I have seen in all of the Caribbean and Central America.
Google Cormier as well as the hotels listed in the other postings to see additional photos and reviews. The Mont Joli has nice, simple rooms and a nice pool with a killer view of the bay as the hotel is slightly above the city. If you would like to rent a nice small cabana inside of Labadee, PM me and I will send you the contact info for a nice Canadian man that rents properties there.
If you are referencing the US Gov Travel Warnings, Haiti will never be safe to visit. I suggest that you find a contact that could guide you in the right direction. Would be happy to assist!