I only had the chance to try Rosetta stone for Japanese and it was kind of bleh.
I'd say got for a regular textbook, good if it has some audio and some exercises with answers. I also prefer regular schoolbooks for kids, the ones for adults are so boring (plus crash-courses can be very superficial and university material too demanding).
And yeah, do watch stuff in Spanish. You'll start to pick up stuff. Back in the 90s when anime in English was rare, I watched it in Italian for about 2-3 years. I had no background in any Romance language, never picked up a grammar or a dictionary, never studied it, but by the end of the first year I understood most of what was being said and even now after a huge hiatus from using the language I'm absolutely fine with listening, decent at reading and somewhat fine with speaking (and I suppose I could easily fix the latter by spending a couple of months in Italy).
