Guinea fowl are superb at spotting and alarming on predators and strangers. They also eat ticks and other bugs. But they can be loud and obnoxious. They are also rather stupid about roads and vehicles.
If you still want some, I have both pearl and lavender guineas, about 4 months old. They outside in a pen with chickens, geese and ducks. You will need to confine them for a while to prevent them from wandering away. A few weeks should do it.