Hi Ally
Believe it or not, I cannot recall if Hotel Marvellous have security boxes and I've stayed there twice, but they do at Arkotal Travel down the road, where you cash your t.cheques. You will have a key to your door, just use your suitcase and forget about it.
I have never felt the need to use them in Arillas. You are in a place where trust, family values, friendliness (need I go on) is very much the norm and I do hope this never changes. Isn't it a shame that the society we live in today in the UK has made us so mis-trusting of each other.
Aly