JJay
We were there in November 95, the safes are located in the wardrobe and are smallish, we put our money jewellery and passports in there, not much else fits possibly a camera, they are free and you set your own combination number to them, they work electronically so probably don't open if there is a power cut.
You will enjoy the PP, we had a great time, we did have a great tour guide in Bellagio though.
Have a Millwoods and Pina Colada slushie for me at the pool bar, a Mimosa or a crazy Canadian in the lobby bar and a nice bottle of cold Cristal at the beer garden, or and I forgot after breakfast at the Coffee bar in the reception a millwoods coffee topped with cinamon.