In general, thinkers of the Enlightenment would have approved of liberalism and would not have liked communism.  They might have approved of socialism, depending on the exact nature of a given socialist system.

The whole idea of liberalism emerged from the Enlightenment.  Enlightenment thinkers were very much dedicated to the idea of the rights of the individual.  It is for this reason that they would have embraced liberalism with its strong emphasis on those rights.  

Communism would have been distasteful to them because of its lack of regard for individual rights.  The idea of a system that guaranteed neither economic nor personal rights would not have met with their approval.  Communism, with its insistence on the inevitable march of history towards a communist system, would have seemed just as illogical to them as a system that insisted on the divine right of kings.  Both would seem to be based on faith and not on reason.

If a socialist system protected people's rights, it might have been acceptable to Enlightenment thinkers.  They might have liked its emphasis on the equality of all people.  However, it would have been important for it to be a democratic form of socialism that guaranteed political and economic rights.