So I live in Barcelona at the moment. I have 10 years of system administration experience and 3 years of devops / sysadmin experience as well. The average salary I am offered when I look around is between 25K and 45K Euros a year. However, I would say the ratio is about 60% For friends and family that are looking it really depends. If you are lucky and have / had a position in certain companies who are well known, you might get into the higher bracket. If you dont, and for example only have a University degree, then expect to start between 15K and 25K (unless from one of the known private schools, in which case you can normally jump to the next bracket).
From what I know, the two places to look are Madrid and Barcelona, but Madrid normally list almost double the amount of jobs that Barcelona does (mainly because a lot of headquarters are located there).
Another important thing that I have notices is that its a lot harder to climb internally in companies here. It depends if the company has American business culture or Spanish (but sometimes it tries to be American but its run in a Spanish way). This is in general over all businesses. My wife is currently working at a call-center and have co-workers who have been in that position for over 10 years. There are basically no way to get promoted, unless you get lucky and someone retires or leaves. I have seen this everywhere, basically no way to really grow, no incentives to grow, an over educated workforce, where the cashier in the supermarket has a masters degree in childcare or similar.
There is a saying here, where they call people "mil eurista" meaning thousand euroist more less. The amount of the working population that earn around 1000e a month is quite high but its something thats accepted here basically. People are not happy about it, but "At least I got a job" attitudes are everywhere.
A last thing, take care regarding any unemployment numbers that appear during the month of May, as thats basically when the tourist season starts. That alone probably employs over 1,000,000 workers during the summer months.