been to Tortola three years in a row for a week, and never were there 4 days in a row with a consistent size, it varied quite a bit in size and conditions.... hard to know what you will get. I went in March each year..
Everyone has already nailed it, but just my confirmation that in the Caribbean, best waves are on Puerto Rico, Dominican Republic, Barbados, and the Caribbean side of Panama and Costa Rica. A lot of people forget about the Caribbean side of Costa Rica and Panama, which can be super good and consistent.
If you look at a map of the Caribbean Islands, you'll see lots of other islands exposed to tons of swell, but most of them suffer from poor bathymetry profiles that dampen much of the swell energy.
Last trip to Tortola we got three major swells in one week. CG was perfect with like 5 people out. Just perfect rights. But friend went down this past winter and got nothing and spent a ton of money. Take plane to St.Thomas and take ferry to Tortola. Apple Bay may be a bit more consistent but just playful tho in my opinion. I would recommend another island as others had mentioned unless you can check the forcast a couple of days ahead of time and book a flight then to St.Thomas. It looks like Spirit airlines has cheap flights to there. Heard Tobago had a good wave. Never been. In Tortola u can stay in CG or Sebatians is really good. Good food and huge lobster dinners. Have fun!