Google these coordinates:
that's the Beach access ramp at the end of International Speedway Blvd. When you're on I-95, get off on exit 261 and go East toward the beach.
At the end of International Speedway Blvd is a ramp to get onto the beach. Go down it, pay the entrance fee (I think $5), then go right on the beach. You'll see the line of cars a little bit down on the right side