Flyer, I learned Spanish when I was 17-18 by taking 6 months of immersion in Mexico and living with a Mexican family. It was great, and my school is still operating almost 20 years later with some of the same staff.
They can set you up in a program with 3-4 hours a day of private lessons + 1-2 more of group lessons, and live with a local family that cooks for you three times a day, for a very reasonable price.
It was about $600 a month all in in late 90’s prices, I’d guess more like $1200-1500 for a month now.