How likely is it to get Rabies in countries such as Tanzania and Kenya?

Hopefully I'll be going to Africa next month to do some voluntary First Aid work. I'm getting a Yellow Fever injection done next week and it was recommended that I get injected for Rabies as well. However, the injections are expensive and I'm just a broke student, not to mention that 3 injections are needed and I'll be leaving before the time of the third one. I thought I might just take my chances and go without the injection, hoping that I don't get bitten. How likely is it to get Rabies in these countries? Is it a very fatal illness? Will I survive it if I get bitten so long as I recognize the symptoms and get to the hospital before it's too late? I know a girl who went to Ghana without Rabies injections and nothing happened to her.