I did. I was really interested in Chinese (still am) and worked like a demon. I had the advantage that I was in Taiwan, surrounded by the language.
When I came to Taiwan, I didn’t know much more than 我、你、他、好、不好, but I saw people who had been here for three or four years still struggling with a dictionary. I thought, That’s not for me. I was also extremely lucky that a month or two after I started learning Chinese, Liang Shihchiu published his wonderful Chinese English dictionary.
During that year, I woke up and walked to the New Park to study Mantis and Shaolin. Then back to the International House to study before lunch, lunch, class, study, dinner, study. I did little else than that, aside from vacations when I ran off into the mountains, the deeper the better. To get there I hitchhiked and usually got rides from bored truck drivers who wanted somebody to shoot the breeze with. That was always a good reality check on what I learned at the Mandarin Center.
How hard did I work? At the end of that year, you could give me any Chinese character and I could open my Liang Shihchiu dictionary to within five pages of it.
No Westerner had entered a local university as a freshman. There was a lot of paperwork involved, but the Ministry of Education decided to give me a chance, and admitted me to the Chinese Lit department at NTNU (臺師大). I will never forget my horror during my first class, 李曰剛老師教韓非子 Han Feizi taught by a professor Li Yuehkang, who had such a heavy Jiangsu accent that I simply couldn’t understand him. I asked the girl next to me, obviously a local, “What can I do? I don’t understand him.” She smiled and said, “Nobody does.” We would all take notes and share, and usually work out what was going on.
Anyway, I continued working like a demon, especially when I discovered Confucius and the Hundred Schools, and etymology. But yeah, it is possible to learn Chinese in one year before starting your major in a Chinese university. It takes a lot of work, but it is rewarding almost beyond belief.