Money and Credit Cards
First and most importantly Cash is king on the Camino. Most albergues and many bars and restaurants on the Camino work on a cash basis. The currency of Spain, France, and Portugal is the Euro. In larger cities and towns credit cards may be accepted but I would plan on using cash. So that brings up a big question. Do I carry a large amount of cash with me? Not necessarily. Their are ATM’s in all large towns and many smaller towns but certainly not in small villages. Typically pilgrims carry 200€ or 300€ at a time. Stopping along the way every several days to take more from the ATM machines. It is important to have an account at a financial institution that allows you to use your ATM card with no foreign transaction fee. A foreign transaction fee is a charge of about 3% added to your withdrawal. I know that Charles Schwab and Fidelity offer checking accounts with no monthly fee and do not charge a foreign transaction fee. I am not endorsing either of these simply passing on information.
Camino Safety
The Camino is a relatively safe place. However, it is important to take precautions with our valuables. That means money, credit cards, your passport, your pilgrims credential and any electronics or cameras. So what do we mean by precautions. That means that you NEVER let these things out of your sight. You take them with you to the bathroom in the middle of the night, you take them into the shower, you take them with you everywhere you go at all times. Violent crime is rare on the Camino but property crime happens. The best way it has been described to me is that if you would not leave whatever it is on a table in a food court in the US and walk away from it don’t leave it in Spain. All of that being said it should be perfectly OK to leave your backpack in the albergue while you go out for dinner, sightseeing, or shopping.
Make sure that you have some type of waterproof container, such as a large ziplock bag with you so that you can take your valuables into the shower with you.
So far as personal safety is concerned. You just need to pay attention to your surroundings. Spain seems to be a safe place and especially the Camino but of course things happen when we get careless.