We will be arriving in St. Martin in two weeks on our first return trip since Irma. We normally stay on Simpson Bay Beach, but this time will be staying in Porto Cupecoy. We always rent a car, and this time is no exception, since we typically stay for 2 to 3 weeks and it is not only much more convenient but usually cheaper, too. We have never used the taxis, but there have been several posts on this topic on the TA St. Martin/St Maarten forum over the years. Taxis are readily available right outside arrivals, as stmartinfan points out. I have not been able to locate a recent fare chart online, but found this helpful commentary from Frommer (not sure how recent it is):
Here's a guide to getting around in St. Maarten/St. Martin - everything you need to know.
www.frommers.com
The official fares are for two passengers during regular hours. Late evening or late night fares are higher. They indicate the first piece of luggage is included, but there is a $1 surcharge for additional pieces. Divi Little Bay is probably in the Philipsburg zone, so it appears the base price would be $15 USD from SXM. If you are intending to stay mostly close to the resort, the taxi could well save you some money. The buses are small passenger vans with set routes, but not set times. They are mostly designed for locals to go about their business, so with luggage they are probably not that convenient. They are cheap, so might be an option to go somewhere while on the island. They have a sign in the front indicating their ultimate destination. You just flag them down, is how I understand it works. According to Frommer the cost is $2 per trip per person.