is a nice anchorage with good holding and the "PAYS" (Portsmouth Association of Yacht Services) boat boys have a security dinghy
that goes around at night to make sure that the visiting yachts aren't pilfered from. Portsmouth is a good place to start exploring the island and Dominica
is one of my favorite places in the Caribbean
as it is still relatively unspoilt.
There are few places ashore in either Portsmouth or down island in Roseau that cater to visiting tourists; but the local restaurants do offer tasty local food
When approaching Portsmouth one of the local boat boys will come out to offer services. Unless you already have someone that you'd like to use this one will come to you after you anchor
and see what you may want. Most of them are certified Indian River guides and that is worth a trip; they'll also arrange rental cars and anything else you might want.
The PAYS folks have a once a week BBQ and party ashore that is worth visiting, not only to mix with other cruisers but also to fund the security
boat. The organisation is a good one, since once you've chosen someone you won't be bothered by the others at all. There are a couple of people on pirogues selling fruits and the like who go around the anchorage, but it isn't particularly bad.
Take a look at my Dominica page at https://www.sv-zanshin.com/countries/dominica.php