You can cook. But also plenty of good/cheap eats can be found outside the home, especially in Osaka. You just have to get there and have some local people show you around the local eateries. You can even have 3 meals a day at the convenience store for about $10-20USD/day lol. Breakfast: bread with filling+milk. Lunch: ramen/curry. Dinner: Bento.

It really depends on what you eat, but I think you can scrape by with $15 a day if you really had to. Perhaps less but I can't get enough of the food when I'm there so put me in a convenience store I'm going off :)

As for local travel, get train/bus passes. After you figure out your regular travel routes, then go to the pertinent ticket office. Keep in mind, it's not one train/subway system. You have JR (public) and various private railways. If you're in downtown Osaka, if you include subways I think there's about 5 different rail systems and each have their own ticketing office. I suggest your local friends to help you with that.

Also if you have to go through Umeda (one of the larger train stations in Osaka where many trains/subways converge)....it's a megamaze of confusion. Even locals get confused witht he many train systems and labyrynth the station itself is.

Just be patient.

Good luck.

Thanks for the great ideas, I really appriciate the help! Keep them coming!

hello,
I dont know whether you are in Japan already, but I will throw my two sense on this question. I was in Japan three weeks ago. The food is much cheaper than here in Los Angeles, interms of eating out. Please keep in mind that eating portions are not like American restaurants. Actually, I found that places where rice topped with beef was sold was more reasonable than Los Angeles. On average, you might be able to spend less than 5 bucks for breakfast. I mean a decent breakfast where you get toast, eggs, ham and orange juice. Japan has many bakeries and inside you can find nice pastries that make good breakfasts. Lunch is just about the same too. I highly recommend hitting up supermarkets, because they usually sell food that is already made and warm.
I found Japan quite resonable. However transportation in Japan is quite expensive and I would not be surprised if rates went up soon. I stayed at my friends house for two weeks and ened up spending more on subway and bus than other daily necesities. So, my suggestion. If something isnt so far away, then walk. Don't settle for fast food joints, because usually these might be a little bit more pricier. If you walk around and search you will find something reasonable, always. Rice will be a god send when you just want your tummy to feel full. Ah, yes, one thing that is cheap and good is making rice at home and buying ready to eat curry. In Japan, curry comes in many flavors.
I found that sushi and sashimi are quite cheap compared to Los Angeles, when bought at a store.

good day, and good travels!

Armando