The roads aren't marked all that well but getting lost is hard to do - eventually if you keep driving you'll find you way back to the ship. The cab fare just going to Orient beach & returning back to the ship is probably only slightly less than a car rental for the day.
Maho beach is a neat stop for a while on the return to the ship where you can watch the planes landing right over you head. Maho beach
Just leave enough time to get back to the ship since they've been working on the roads for as long as I can remember & you usually get caught in a 30 minute traffic tie up at 4 PM.