Hi Zuzana
Your sense of security will probably change during your caminho. I think most of us start by squirrelling our valuables bag into our sleeping bag for the first few nights. But then when you realise that you are seeing mostly the same people day after day and they are going to the same place as you, and that some of them just leave their £600 iphones charging while they shower or go off somewhere, you tend to relax. And you find you get to know some pilgrims and trust them and start to feel you don't need to clutch everything to your person the whole time as you're all informally looking out for each other. If you have to take a great big SLR camera, then Iriebabel's strategy (above) sounds as good as any I can think of.
BTW the showers are usually in enclosures with doors where you have just enough room to hang up your clothes etc inside and a normal camera case should be fine in there as well, if you decide your camera is coming with you.
I think that over time pilgrims come to sense that the theft of valuables is highly unlikely in pilgrim hostels amongst people that they've largely come to know. And they relax accordingly. The trick is to be aware when that situation changes, for instance when you come back to the big cities. I remember a couple of cases of thieves getting into the main albergue in Leon a few years back and cleaning the place out. So the key is to always assess the situation around you and adjust accordingly - and make friends!
Cheers, tom