Fast food is here, but it is nowhere near as prevalent as it is in the States. The only American chains with a presence are McDonald's and Kentucky Fried Chicken. I have seen a few shuttered Subway locations, so evidently South Africans are pretty smart and ran them out of business. But, you don't see fast food on every corner. There are 93% fewer McDonald's here per capita than in the States, so you have to plan ahead for your McNuggets fix.
The quick-serve restaurant phenomenon that has taken over the US hasn't really reached South Africa. If you want something more upscale than fast food, it's pretty much limited to a sit-down restaurant. Nando's is the one exception; it's a South African chain that serves Mozambiquan/Portuguese-style grilled chicken restaurants with the extra-spicy Peri Peri sauce. The chain is quite popular, not only in South Africa, but actually in about 20 countries world-wide, including a handful of branches in the Washington DC area.
There is a pretty good selection of types of sit-down restaurants, with plenty of Italian and Indian choices, and many other standard choices, like seafood, steakhouses and various cafes. Mexican food seems to be the hardest to find, and the embassy even offers special days where staff can meet with a local importer to buy Mexican ingredients, since they aren't really carried widely in the grocery stores either.
It is pretty standard practice to make a dinner reservation no matter where you eat in a sit-down establishment, even in the middle of the week. People don't seem to really just wait around for a table like we might.
Dining out is definitely a bit of a bargain for Americans. Menu prices are similar or a bit cheaper than back home, but the sales tax is already included, and the standard for tipping here is just 10%, so by the time you settle up, you've saved a bit of money, especially if you had drinks. Alcohol is noticeably cheaper, and for mixed drinks, you are just charged by the ingredient. A Rum & Coke is about $1.50 for the shot of rum, and $1.50 for the Coca-Cola, and a glass of house wine is usually just $2.50 to $4.
Soft drinks don't come with free refills, unless you "upgrade" to the bottomless sodas that a few restaurants offer. I'm a big Iced Coffee fan, but here they like to serve "American-style Iced Coffee", which to them means a glass of black coffee, with a scoop of vanilla ice cream and some whipped cream. But for after-dinner, they have an interesting drink called a Dom Pedro. It's basically almost-melted vanilla ice cream mixed with the liqueur of your choice, like Bailey's or Amaretto or Amarula. Basically, an alcoholic milkshake that I think that would be a big hit stateside.
There are a few favorite dishes that you find everywhere...grilled Haloumi cheese (a nice Cypriot cheese that's a bit salty and can be grilled without melting) and some version of Chicken Livers seems to be mandatory on every menu. Otherwise, the menus usually have a nice variety and portion sizes are a bit smaller than in the States, but still ample.
When it comes time to pay, you ask for the bill (which always arrives with mints), and you fill in the tip amount and then let them know if you are paying with a card, and if so, they bring a wireless machine to your table. All the credit and debit cards issued here have smart chips in them, so signatures aren't necessary. Your card is inserted in the machine, and you key in your PIN and the receipt is printed right away, and the card never leaves your sight.
It's not clear if this system will ever make its way to the US; Visa and MasterCard are trying to move our retailers to the Chip and PIN system before 2016, but the cost to replace all those credit card machines in the US is astronomical. Some people think we will just skip over this cycle and move directly to mobile payment options, using your cellphone to pay, like you already can at Starbucks.
Here's a link to a menu at a local chain restaurant, Mugg & Bean, that has a nice selection of items. The prices are in Rand, of course, so if you divide by 10, you'd have the effective price in US dollars, before tax and tip.