I can only echo what it says in the Wikitravel article about the Entebbe Botanical Gardens, "the unofficial guides at the gardens were unusually aggressive for Uganda, and if you engage their services you should agree on a reasonable price beforehand." As soon as we came into sight of the entrance we were pounced on by a guide, but all we wanted was to idle away the last day of our trip in peaceful and pleasant surroundings so we said no.
In retrospect, it might have been more peaceful to have said yes, as thereafter we were approached every five minutes or so by someone wanting to explain things to us. Pleasant, yes; peaceful, no. In fact the whole of Entebbe felt a bit edgy, and was the only place in Uganda where I felt at all uncomfortable. Perhaps I was just ready to go home.
Good collection of plants from around the world, teeming with birds, and home to a troupe of colobus monkeys. The guides also claim that the gardens were used as a location for some of the early Tarzan films. However, this has never been verified.