St. T is a miserable tourist trap designed to fleece cruse customers(and there are plenty of them) out of cash.
mid jan is sort of high season. can you still get reservations? do you have a passport?
are you leaving from PDX? if so, it is a seriously long trip to the carab islands. you will spend more time in the air than in the water. go to safe mexico. costs less, takes much less time. beaches are great.
aruba, bonair, curaco, roatan, st johns, bvi all have nice beaches. it is hot even in jan.
you can stay cheap in decent place with beautiful beach in bvi. just look at the edges.