I can recommend OLSA 100%! Through their programs, I learned Spanish in very short time, and reached a level that is enough to have great conversations with locals. Mind you, when I started going to OLSA, my Spanish skills were close to 0.
The classes are very fun and the teachers are excellent at keeping the classes entertaining, yet highly productive. They don't only teach conversational Spanish, but also the grammar.
Whether you are a beginner or need to polish your existing Spanish skills, the courses offered work for any level.
And all of this comes at a very competitive price! Other Spanish schools I looked at seemed to be way more expensive.
All in all, highly recommended!