I disagree. Those dropouts are horizontal enough for an SS/FG conversion. I've converted a few mountain bikes to SS and one to FG. Two of them have had much more vertical dropouts and they've all worked fine. You just have to be picky about gearing. Not all choices will work.

IMO, fixed gear is more for "fun" than anything else, but the guys over in the SS/FG section would disagree with me. I rode FG for about a year before deciding I didn't like it and switched my bikes to SS. The nice thing about SS is that it only requires a couple cheap parts, whereas a "correct" fixed conversion requires a new rear wheel to thread on a cog and lockring. The rear wheel is almost always the most expensive part.

Slicks would help that bike a lot in city riding.