I'm basing this impression on the incident at the end of the episode Profit and Loss
, where he shoots a Cardassian military officer in order to give the dissident professor and her students a chance to get away. He then explains to Quark that he did it out of love for his homeworld.
This says quite plainly to me that he sympathises with the dissidents. The actor who played him certainly seemed to have it in his head that Garak was something of a reformist.
What does everybody else think?