I moved to Madrid this past December, and have thought about this question quite a bit. TL;DR: if you can work remotely and live in Spain you'll have a great life. Cost of living is 1/3-1/2 of SF or NYC, but incomes in tech are also 1/3 to 1/2.
More specifically:
1. Language in tech is not a big issue if you speak English. The work and the documentation will largely be in English and most of your young co-workers will speak English.
2. Remote work in Madrid is easy: there are lots of co-working places, rents are cheap, high-speed internet is relatively ubiquitous, and transportation to the U.S. and other parts of Europe is accessible.
3. Expect Madrid's infrastructure and startup scene to be about 5 years behind New York's in most ways. (Except access to capital - Madrid's way behind on that front).
4. In terms of local opportunities in Madrid: There are both Google and Amazon offices here, most of the big bank headquarters, and lots of freelance opportunities for local companies. Startups exist, but there aren't as many as you'd find in larger tech-hubs - founders don't tend to be very sophisticated, but there are lots of exceptions.
5. Job security is much more important and more expected for the Spanish - and it's a philosophy that's a bit rough for the startup community. It's harder to get a job because people don't quit and companies don't fire them as quickly AND it's harder to start something because each hire becomes a potentially crippling liability if you run into cash-flow problems.
6. The Spanish value work/life-balance. Siestas aren't as ubiquitous as they used to be, but there are lots ways that the Spanish still find to enjoy life - younger people with full-time jobs seem to have time and resources for hobbies, courses, and travel as well as plenty of time for family.
More specifically: 1. Language in tech is not a big issue if you speak English. The work and the documentation will largely be in English and most of your young co-workers will speak English. 2. Remote work in Madrid is easy: there are lots of co-working places, rents are cheap, high-speed internet is relatively ubiquitous, and transportation to the U.S. and other parts of Europe is accessible. 3. Expect Madrid's infrastructure and startup scene to be about 5 years behind New York's in most ways. (Except access to capital - Madrid's way behind on that front). 4. In terms of local opportunities in Madrid: There are both Google and Amazon offices here, most of the big bank headquarters, and lots of freelance opportunities for local companies. Startups exist, but there aren't as many as you'd find in larger tech-hubs - founders don't tend to be very sophisticated, but there are lots of exceptions. 5. Job security is much more important and more expected for the Spanish - and it's a philosophy that's a bit rough for the startup community. It's harder to get a job because people don't quit and companies don't fire them as quickly AND it's harder to start something because each hire becomes a potentially crippling liability if you run into cash-flow problems. 6. The Spanish value work/life-balance. Siestas aren't as ubiquitous as they used to be, but there are lots ways that the Spanish still find to enjoy life - younger people with full-time jobs seem to have time and resources for hobbies, courses, and travel as well as plenty of time for family.