Learning to speak Arabic, just like learning to speak any language, depends mostly on the student's willingness to experiment, engage native speakers and, of course, study . 

However, based on Saifi's experience it usually takes the student 60 hours of class time to be able to accomplish all daily tasks in Arabic and carry on basic conversations on social topics.  After about 180 hours of class time (6 months taking accelerated classes) students are able to converse on a variety of subjects in some depth... and even fool some native speakers with their accent.  See our proficiency chart for more detailed info.