Translation:If you learn Swahili, you will be able to talk with Tanzanians
In English, "can" and "be able to" are synonymous. Kuweza should be able to be translated with either. Further, I agree with the other commentators that "talk to" or "talk with" are also good translations for kuzungumza
"Will can", of course. "You will can peas if you work in a conserve factory." Just kidding. Cheers.