Unless you are hopelessly lost in the bush somewhere, you will probably be able to find someone who speaks English. Attempts to use Swahili are generally warmly received and can often help in conversations. Despite the widespread use of Swahili, most Kenyans have their own tribal language and view Swahili as a foreign language, as they do English. Swahili is not a difficult language. It is pronounced pretty much as it looks.
Nothing is silent and there are no real tricks.
Below is a small, categorized list of some words that might be helpful, as well as some online resources and dictionaries . Kiswahili Home Page - A good tutorial which is split into chapters. Includes a short history of the Kiswahili language.