I am learning Spanish on Duolingo right now. I have been doing it for about a year. I took Latin in HS, and French in college, and grew up in a Hispanic part of Miami, so the language mechanics are familiar.

I was so much more fluent this summer in Spain than I expected. Duolingo has been really good. My Spanish is no longer a grammatical mess, and I know a lot more vocabulary.

My goal is to live in Spain part time when I retire (in about 4 years) and I would love to be semi fluent by then.

I think Spanish is very useful to know living in the US as well. I spoke a lot more and understood more in Miami my last visit. But, boy do they talk fast in Miami Spanish.

no matter what you pick, consider Duolingo as a source. It is really good.