hi Estee
dont worry about the language barrier cause here almost everyone speacks english and even if dont, they are very friendly. language wont be an issue.
you also will find a lot of south african people living and running bussiness here. here you will find places like nandos, mimo, blue ocean, supermarkets like game, pick and pay, whooleworth food and other many places. so im sure you will feel at home.
about the food prices, i would say, it depends on what and where you buy it. some places can be very expensive and others cheaper.
im sure you will do just fine. but to start you can advertise some of your products at mundos restaurant at julius neyerere avenue. its a very good place to advertise your produts cause there are always busy with commemorations of all kind and they also advertise other people products.
katucha