Great question! That depends on several factors, but generally we see folks taking at least 2 classes per week be able to hold a 5-10 minute conversation with a native speaker, without any aides or help, but only using the present tense.
A few factors that can affect your fluency:
1) Rate of learning - if you learn pretty quick, you can take more lesson concepts per session.
2) # of classes per week - we recommend at least 2 per week, but many students do 3 or more.
3) Speaking practice - your fluency will also depend on how frequently you talk to other in Spanish, and how consistent you are with that practice.