If you're thinking about investing in Barcelona, and having fears about the separatist movement: don't worry, it is not going to happen. In that regard Barcelona is pretty much like London: separatists are a minority, being the separatist power in the countryside. So before the Catalan region of Spain becoming independent, Barcelona would remain as part of Spain (in the improbable case of all Spanish citizens agreed about allowing a "Clarity Act" like in Canada, so if Spain could be divided, any separatist region could be divided as well -that would be going "nuclear" against separatists that consider the Catalan region of Spain as "indivisible"-). So independence chance is 0, in my opinion. I hope Catalan nationalism will reduce its influence once their leaders pass through the court (corruption cases), and everything gets back to normal, with bilingüism/trilingüism in the schools and public administration, instead of current de-facto Catalan monolingual stuff in the public sphere. If after that you still have doubts, invest in Madrid first, and think about Barcelona once the political scene gets more rational (I love Barcelona, don't get me wrong).
I wouldn't discourage the OP like that. Most of Barcelona's huge immigrant population -- Romanian, Bulgarian, Pakistani, etc. -- never learns Catalan even after two decades living there. They manage perfectly fine without Catalan, and become proficient in Castilian instead. (Of course, their children learn Catalan as they go through the local school system.)
Of course, I think it would be rude for a white collar person like the OP to move to Barcelona and never learn Catalan, but he could certainly move there and get by with Castilian for the first several months.
What type of jobs is expected for them?
I do get the feeling, at least in Barcelona, that the preference is Catalan > English > Spanish. I've only visited as a tourist though; so I don't know how much of that carries over to the business world.
I find that very hard to believe, but if it did happen, it's either a joke or a one-off case.
I can tell you that you are highly misinformed if you think the preference is Catalan > English > Spanish :)
Hence, the usual result is that whenever you get spoken at in "broken" spanish you instinctively switch to english. Hell, I've went on to work on tech circles, and I still feel more comfortable speaking english with people who have a strong accent, even if they are germans/whatever and english is not their native language either!
With catalan it is a different situation. Anyone trying to speak catalan is not just trying to survive (they would do that in spanish!). They are actively trying to learn your native language, and it makes you and your culture feel respected by that person. In such a situation, you do your best to try to understand that person and help him improve further without being pedantic.
For a comparison, I've felt a similar "gratitude/respect reaction" when trying to say a few things in Gaelic while I was visiting northern Ireland.
This is not granted always. It depends on the people.
The problem is that you are trying to learn spanish being inmersed at the same time in another similar language but with different orthographic and grammatical rules. And you see examples of the non-spanish version everywhere in your journey. Should you use a 'B' or a 'V' for that word?. Sounds the same but is often the opposite in the two languages. Lots of people have problems with that without even noticing.
Just to clarify, if you tell someone you didn't understand their initial answer, they won't have any problem changing to Spanish.
Unless you want to pass for the equivalent of a redneck when doing bussiness in lots of American countries and also in most spanish provinces, you should remember that those words must be written in spanish as: alcoba, almíbar, gabardina, abortar, verruga, vivac, automóvil, probar, reventar, verbena, está, China and correr (with word stress in the e this time), for example.
And would be good to remind also that sometimes the same concept is treated as masculine in Spanish but is feminine in Catalán (or the opposite case). Unlike english we use different articles for masculine and femenine words so this is important. Would be like using "she" when talking about our manager John.
And this is only a small part of the complete bobby trap list.
In absolute terms, but take in mind that life in Spain can be much less expensive than living in Berlin or Paris. It depends on the area and the job.
> I'm currently functional in Spanish but I have a long way to go until fluency. That's one of my goals in moving to Spain
Madrid is the right option then. Has worst climate with more hot in summer and colder in winter, and is as stressful as any other big city, but is a much more easier place to learn spanish, and (probably) an easier place for a foreigner to mix with the locals. Barcelona uses heavily Catalonian language for all: trafic signs, street posters, commerce, casual conversation, television, politics... all.
On the other hand, if you can find work in any of the other "big/but not so big" province capitals (or can do remote work) maybe you should consider it. Smaller the city, worst pay, but much better life quality. The climate is better around the coast, as usual.
> How limiting is it to not be fluent enough in Spanish for use at work
As long as you speak english and know your stuff, should not be a big problem. English is worshipped (an old national inferiority complex) and in fact could be much more difficult to you to find a job in Spain if you were Spaniard.