Don't go swimming with your bikes and don't lay any oiled/greased parts in the sand and they will be fine. Road grim causes more harm to my bikes than the ocean air (I do keep them clean).

If you decide to rent, check out the rental company with the local Better Business Bureau. One scam is that you pay replacement price if the bike gets stolen. The rental Co. gives you a useless lock (just to be safe). Thief cuts useless lock, steals bike, sells bike back to rental Co., you pay rental Co. full price for bike and the circle begins again.

Enjoy the trip!