You should take which restaurants to go to with a grain of salt. If you're going to be there for three weeks, it gives you a lot of time to explore. When I went to Hong Kong a few years ago, I went to a few highly recommended restaurants and invariably was disappointed.

When you have free time, catch the kanjo-sen that circles the city and get off at almost any stop. There will always be decent restaurants near a station. It comes down to what you are looking for. If you're looking for high-end restaurants that cost $40-50 a meal, well, they are not hard to find, in my opinion. It's those little hole-in-the-walls that have that special combination of value, taste, ambience, etc., that makes it memorable.

I know near Tsuruhashi station there's a really great robatayaki that I enjoy going to every time I'm in Osaka but I'm sure there's dozens of similar restaurants like them.

I think half the fun of going into a new place is simply enjoying it for what it is. Sometimes it's great, sometimes it's not. But you almost have to rely upon your own standards of what is good and what is not.

Good luck. . . .