Play golf. There are so many courses to play and so little time! If you go in March, the prices are so cheap for rounds of golf that you can play 36 holes a day for the price of 18.
Quick Tips: At this time of year, everything is cheap in Myrtle Beach. It's a great time to go, if you don't need 80-degree temps. Get an entertaiment book! This will save you plenty of money for dining over the span of a week... also allows you to try new restaurants.
Best Way To Get Around: Rent a car... especially if you plan on playing golf. There are so many courses, and they are all spread out, so there really isn't any other way to get around.