We hired a car last year and went to Maho Beach to watch the aircraft. It was great fun. We didn't get involved in the whole getting blown across the beach and hanging onto the fence, but sat at the Sunset Bar and got loads of great photos.
It really was a fun day out, it is amazing seeing the aircraft flying so low.
We just wandered up the town in the afternoon, with the compulsory trip to Diamonds International

how much do I love my DH

lol
You have to be careful if you go across to Maho Beach as apparently the bridge opens in the afternoon to let the shipping traffic through and holds up all the vehicles in the process. All the websites warn you to get back across to the main town as early as possible in the afternoon so that you don't get stuck in the traffic and miss ship boarding time... apparently its happened before
We had no trouble, we waited until we saw a 747 and then left to be on the safe side.
All in all a fantastic day