To add to and expound on what has already been said, St. Kitts is a nice day trip if you want to golf in more pristine conditions but it won't be cheap - but when is golf ever?
Factor in the flight/transportations expenses along with the golf fees themselves and lunch and all, and the departures fees and taxes and it becomes an expensive day. We haven't been to St. Kitts recently but they took their golfing very seriously in years gone by. If you have time afterwards, St. Kitts is one very beautiful island with a lot to see and experience. Beaches aren't up to the level of SXM IMO, but the general scenery surpasses that of SXM and is, again IMO, extraordinary and well worth the trip even w/o the golfing.
Back to Mullet. My SIL golfs at Mullet at least a few times every year and often times their spring trip to conincide with the St. Maarten open in April. The course itself isn't well maintained, has no watering system and the greens are usually a mess but if you hve a sense of humor and want to kick back, have some fun and play what once was one of the best courses in that part of the Caribbean, you'll probably enjoy it. And if you go knowing and decide to play anyway, you will definitely have a golfing story to share after the fact. He has fun with it every year and yes, he brings his clubs, although not his good ones, and he enjoys every round he plays as does my grandson.
If you choose NOT to go the St. Kitts route, truthfully, for one or two rounds on Mullet as it is today, I wouldn't recommend going to the trouble and expense of bringing clubs and yes, you can rent a set. That would be my best suggestion if only playing a round or two at Mullet.
And btw, we have a timeshare that overlooks much of the course and are there for 2 t 3 weeks a year over multiple seasons - people do play all day every day, guests and islanders alike, and they seem to have fun with it.