You can either hitch to Cinnamon Bay from Cruz Bay on St. John or you can take a taxi. Just ask them for Cinnamon Bay and you're there. Cinnamon Bay is a popular campground on St. John...you can even rent a campsite for pretty cheap. It's pretty close to Maho Bay which is in my Top 10 most beautiful beaches. You can walk there...but its a haul.
NOTE: IF HITCHING>>>>DO NOT USE THUMB!!!!!! POINT IN THE DIRECTION YOU WANT TO GO! BE FRIENDLY AND SMILE.
Unfortunately...most of the surf spots in St. John can only be surfed during storm swells. But if you get a good weather report and talk to some local surfers (go to maho bay campgrounds or cinnamon bay camgrounds and ask someone there) you can catch the swell in some crystal water and the waves are glassy and beautiful. Every time I've surfed it, I leave with a smile on my face. The view from the line-up is nothing but palms and babes. Its a great beach.