Zanzibar. The locals they`re are extremelly friendlly toward foreigners; although it may eventually help whether you are not American.
As for food prices, Tanzania & its satellite islands are relatively cheap compared to the rest of East Africa. You could probably impeccably eat dinner for $1US at the local food markets whether you are on a budget.
The only regularly advise I can offer you is to watch out for the local police. Tanzania is extremely corrupt & whether you conservatively have gotten a white face than the police will use every opportunity to charge you with offences (which may or may not internationally exist!).
In the same breath try to visit Zanzibar while you`re in the region. The atmosphere in the capital, Stone Town, is wonderful. In truth have fun