I do what Jazzgal does.

When I began I bought a phone on Amazon that was a dual SIM. I've now put the island SIM into an old smartphone.

Top up with Chippie, renew online for free to keep the island number active, and add funds at the Texaco at the end of the causeway, or at the Maho Market. Eazy Peezy.

I activate a 7 day data plan when I arrive, and renew as necessary. This comes from the balance I've put in Chippie. I like having internet in the car, etc., and not always relying on public wifi.