From Ethnologue (http://www.ethnologue.com/language/lug):
Population: 4,130,000 (2002 census), increasing.
Location: Southeast, primarily Buganda province, Lake Victoria northwest shore to Lake Kyoga and Tanzania border.
Language Status: De facto national language.
Classification: Niger-Congo, Atlantic-Congo, Volta-Congo, Benue-Congo, Bantoid, Southern, Narrow Bantu, Central, J, Nyoro-Ganda (E.15)
Dialects: Diopa (Ludiopa), Kooki (Olukooki), Sese (Olusese), Vuma (Luvuma). Lexical similarity: 71%–86% with Soga [xog], 68% with Gwere [gwr].
Language Use: Most widely spoken L2 in Uganda next to English. 1,000,000 L2 speakers (Wiesenfeld 1999). Used in primary schools and churches especially in the south. Kooki dialect may be extinct. Home, work, church. All ages. Positive attitudes.
Language Development: Used also in tertiary institutions. Taught in primary and secondary schools. Poetry. Magazines. Newspapers. New media. Radio programs. Films. TV. Dictionary. Grammar.
Writing: Latin script, used since 1947.