Were magnetic monopoles created before, during or after inflation? In the case that magnetic monopoles exist, when were they created? I thought that all particles were created after inflation, but I've read some comments recently that hint at a pre-inflationary creation of magnetic monopoles.
Before. The point is that there were too many predicted, and no concept of inflation yet. Here is a reference that doesn't just gloss over it.

Here is the original paper by Guth, and physics.SE has a nice drawing of the same timeline shown on that page. (Original here)

You ought to try that physics.SE thread and continue there for more details.