Playa de las Cruces is an extension to the beach of Vargas. I never realised there was a difference and always called the whole thing Playa Vargas as do most people but officially the first small cove as you arrive is Playa de Vargas then the long stretch (1 kilometer maybe) of pebble beach after that is "Playa de las Cruces".
First thing to bear in mind is that there's almost always a strong wind blowing here, secondly for most of the year this is a pebble beach and not easy to get in and out of the water. I have to check/update as I'm told around September to November when there's a low tide the shoreline is sandy but I've only ever been there when there were big pebbles.
This is a great beach if you like wind-surfing or kite-surfing. The first half is taken over by the windsurfers and the second half by the kite surfers. They don't seem to mix, I guess there's a technical reason for that? It's all quite spectacular to watch.
If you were to walk to the far end of the beach and over the hill you'd arrive at a small, sandy cove of "Playa de los Tres Peos" which is a beautiful (if still windy) beach to spend the day on.
There's plenty of parking and a few meters before you arrive there's a very well equipped camp site (Camping Vargas) where you can grab something to eat and drink.
Getting here you need to take exit 25 off the GC1 motorway then head north along the GC-191 to the roundabout with the windurf boards (can't miss it, the sails must be 4 meters tall). Turnb right/first exit there and carry on straight to the end of the road.