I have signed in the white border of hinge mounted, overmatted color (yech!) glossies with various fine point felt style pens. This is not, of course, archival, but neither are the prints, so I don't fret over it.

The situation is quite different with archivally processed monochrome prints. Even if you choose not to dry mount, signing on the front of the print itself is widely considered to be gauche. Sign somewhere immediately close to the print on the mat, preferably in pencil, whichever mounting procedure you choose. But also, and this is more critical than an actual signature, label the print with all suitable identifying provenance information using any of a number of methods searchable elsewhere on this site, either on the back of the print itself if not permanently attached to its mount, or on its mount. If a print is good enough to present (e.g., mount, frame), it should be properly identified. Personally, I also despise signing, but it is a necessary evil.