I had the opportunity to visit LA Tortuga island during my trip to Venezuela and it was worth it. There are a couple of ways to visit the island and one of them is via plane. You can hire a small twin engine plane with other tourists for about $200 and split the costs between you. The other way is via a short 3-day cruise out of Punt Arena.
La Tortuga is nice but no need to detour your plans in Venezuela to see this place. There's nothing to see there but deserted beaches and beautiful at that! The water is turquoise in color and crystal clear which makes snorkeling here a dream. If you look far and away, you will see no one else there... a paradise just for yourself.