Mombasa itself is cheap — street food, matatus and a free walk through Old Town cost almost nothing — but non-resident entry fees at the parks and attractions are several times the resident rate, and they are what actually decides your daily spend.
Madaraka Express (SGR) from Nairobi
Kenya Railways runs the Nairobi–Mombasa train with departures at 08:00, 15:00 and 22:00 from both ends. Economy is KSh1,500 and first class KSh4,500; children aged 3–11 travel at half fare. Book only through the official Kenya Railways site, which warns explicitly against third-party ticket sellers.
Diani Backpackers, Galu Beach
The south coast's main hostel, at 14 KFI Road about five minutes' walk from the sand, with a pool, a bar and camping space. Dorm beds are KSh1,500–1,800 and budget private rooms start around KSh3,000. Getting there from the island means the Likoni ferry and a matatu down through Ukunda.
Matatus, tuk-tuks and the Likoni ferry
Matatus run fixed routes along Digo Road and out to Bamburi and Mtwapa, and tuk-tuks handle short hops — agree the fare before you get in, because it is negotiated, not metered. The Likoni ferry is the only link to the south coast; foot passengers board directly while vehicle queues can be long.
Walk Old Town yourself
The coral-stone quarter between Nkrumah Road and the old harbour — Ndia Kuu, Mbarak Hinawy Road, Government Square — costs nothing to wander, and the carved doors and Omani balconies are the point. Guides offer themselves near the Fort Jesus gate; settle a price first if you want one.
What a day costs
A dorm bed at Diani Backpackers is KSh1,500. The variable is entry fees, where non-residents pay a multiple of the resident price: Nguuni Nature Sanctuary is KSh1,200 against KSh500, Wild Waters KSh2,000 against KSh1,800, Haller Park KSh3,000 against KSh1,000. Plan on roughly KSh4,000–6,000 a day for a bed, street food, local transport and one paid attraction — and the SGR at KSh1,500 on top if you are arriving from Nairobi.