Osaka is considered the culinary capital of Japan, and although it is an expensive country, you do not have to spend a lot to have a good meal! So get out of that hotel restaurant and check out the following options:

Fast food restaurants abound, such as the ubiquitous McDonalds (near every station, it seems), KFC (Kentucky Fried Chicken), or Japanese burger joints such as Mos Burger, Lotteria, and Freshness Burger. (Burger King, Arby's, & Taco Bell do not exist in Osaka, and Wendy's recently closed their Japan outlets.)

Convenience stores (open 24 hours), such as Lawson's, Sunkus, Family Mart, and 7-11 are often the staple of people (even Japanese) who eat on the go. Here you can find all the usual snacks, drinks, etc., from microwave burgers to fried chicken to o-bentos (Japanese lunch boxes), to instant ramen (they even provide hot water!) and all the chocolate, chips, and other junk food you would want! Some even sell beer, wine & sake. You can also buy postage stamps here, as well as fresh socks, underwear, and other such toiletries if the need arises.

There are 24-hour restaurants, called family restaurants, which offer food & drink all day & all night long. They are not all that common, but some of them are Denny's, Royal Host, and Skylark.

 If you want "take-home" Japanese food (other than the above), or are interested in a culinary tour of Japan (highly recommended!), then the best place to go is the B1 (basement) food floor of any major department store (i.e. Daimaru and Sogo in Shinsaibashi, Takashimaya in Namba, Kintetsu in Tennoji, Hanshin and Hankyu in Umeda), where you can see & sometimes even get samples of the foods that Japanese people eat every day at home. Some tourists think this is the highlight of their trip -- and love it more than any temple, shrine, or castle they go to!

 But only eating fast food & "conveni" food would be missing out on more of the culinary delights of Osaka:

  1. First and foremost, if you see a little street stall or shop selling some strange looking cooked balls the size of ping-pong balls, then by all means stop and try some! These are an Osaka delicacy called tako-yaki, which are balls of fried dough with a bit of octopus inside, and covered with some soy sauce, dried fish flakes, and maybe some grated seaweed. (it tastes MUCH better than it sounds!) They usually cost around 500 yen for a batch of 10 or so.
  2. Secondly, another Osaka delicacy is something called oko-no-mi-yaki, which is sometimes translated as Japanese pizza. It looks like a small round thick pizza, but is made mostly of chopped cabbage mixed with egg, and shrimp or pork added in, and then topped with soy sauce, dried fish flakes, and grated seaweed. (And again, tastes better than it sounds......and can be made vegetarian as well.) At some oko-no-mi-yaki restaurants they give you the ingredients and you get to cook it yourself at your table! Note that any versions sold in Tokyo or elsewhere are just not the same!

  3. Thirdly, if you want to have the typical Japanese restaurant experience without having to pay hundreds of dollars, then there are a few good chain restaurants where you can eat for about 3000 yen per person (depending on how much you eat & drink, of course!) There are many local  izakaya or robata which sell typical Japanese food and drink (for those who can speak some Japanese), but the chain restaurants called Murasaki, Tengu, or Yoro-no-taki have an advantage because they have menus with pictures so you can just point to order whatever you want! If you ask your hotel, they can probably direct you to the nearest one. A typical dinner for two will cost 5-6000 yen at such places.

  4. Fourthly, (and especially if you have kids -- they love it!),  just skip the expensive sushi restaurants and ask your hotel for the nearest kai-ten sushi, the shops which sell sushi on conveyor belts, where you just take what you want off the belt (like your luggage at the airport!), and then pay the bill when you leave. Prices vary depending on what you grab off the conveyor belt, but some dishes are as cheap as 100 yen for a plate of 2 pieces of sushi. 

Finally, if you want to find a restaurant with English menus, you can check the website of Certified Perfect English Menu.

For a good overview on where and what to eat in Osaka, check out this Osaka Food Guide.