I travel alone a lot and really enjoy it, and Prague is a great place for a solo
traveller. The walking tour is an excellent idea. Both pubs and restaurants
are fine - take a small phrase book (and amuse the locals). I also like to take a notebook and pen to dinner
with me, as novels tend to take me into their world and away from what is
probably the very interesting place that I am actually physically in at that moment. Writing a description of the room and the food and the other diners
might seem trivial at the time but it's nice to look back on.