Colombian-American here. I wasn’t and still am not fluent in Spanish and I was accepted into a Latin American country for service. When I applied I had maybe an intermediate level of fluency. I don’t know that taking the two Spanish courses is a better alternative to the proficiency exam. Unless you just want the experience of taking the classes. I’m sure it’ll be way more expensive to do that in comparison to the proficiency exam though. I took Spanish classes in high school and then in college through the 2200 level (intermediate). Basically just what I needed to satisfy my degree requirements for a foreign language. A lot of people in my cohort had novice level Spanish and were of course still accepted into the program. I think your Spanish level is only one aspect of your application. You should be sure that you have a solid background related to whatever program you’re applying for. They’re definitely looking for more than just strong language skills.