I stayed at Nungwi, the Northern most town of Zanzibar Island.
Stone Town was and hour and a half's drive away...
not particularly intimidating in daylight, but very crowded...
and impossible to visit without acquiring a guide (whether you want one or not)

The Jozani forest was nearer to 2 hours drive from Nungwi
and a much quieter and more pleasant experience!

The red colobus monkeys were very used to people.
However, a(n unpaid volunteer) guide is useful to find them.