I always recommend the fanar islamic center. You don't just get language but also walk away with a bit of culture too.

This is very important when you consider the high level of diglossia in arabic (language) but also the in seprability of arabic language & culture. Fanar also has the advantage of having an extremely ethnically diverse staff so you are pretty much gauranteed to meet someone with a shared language/ethnicity.

Anyway, it's always nicer to go to a semi-museum than to a dedicated stack of classrooms.