| My two cents: I'd sign up for the mile and be happy with however fast or slow I ran/walked. Running or jogging outdoors is a whole different world from doing the same thing on a treadmill, and I think that running on a beach is even harder still because the sand is so unstable. Try this run just for the heck of it, have fun, want more when it's over, and sign up for a longer race in a couple of months.
The great thing about exercise is that the more you do it, the better you get at it, no matter where you start. Can't say that about everything.
Good luck! | 
