Wurm (1972) and O'Grady et al. (1966) list Mardo as a dialect of the Western Desert language A80, distinct from Martu Wangka A86. Mardo, meaning 'man, people' according to Tonkinson (1991:2), is a name used to refer to a group of people encompassing several dialect groups. The number and identity of these dialect groups varies across the literature. Tonkinson (1991:12) includes Gardujarra A51, Manyjilyjarra A51.1, Budijarra A54, Gurajarra A85 and Giyajarra A52, Bird (2001:1) includes Gardujarra A51, Manjilyjarra A51.1, Putijarra A54, Budijarra A54?, Gurajarra A85 and Warnman A62, while Davenport (2005:ix) says there are eight groups in total.
The language spoken by Martu people is known as Martu Wangka A86, though this name is used in different ways, as a contemporary name of a specific language variety (or communilect) from Jigalong station based on Kartujarra A51, Manjiljarra A51.1 and Putijarra A54 (Marsh 1972, in Thieberger 1993:193, 202), and as an alternative name for various Martu language varieties (Thieberger 1993:194, 202). See and use Martu Wangka A86.
Note that there is another (very similar) name, Maduwongga A6 (Tindale 1974:247), though the location described by Tindale is much further south than that of Martu Wangka A86 so it would appear to be a distinct language variety. There is very little information available about Maduwongga. Some sources (e.g. Oates 1975 and O'Grady et al. 1966) give Maduwonga as an alternative name for Gugada C3, while the location Tindale describes overlaps with the location of Wangkatha A12.
Speaker numbers were measured differently across the censuses and various other sources listed in AUSTLANG. You are encouraged to refer to the sources.
Speaker numbers for ‘NILS 2004’ and ‘2005 estimate’ come from 'Table F.3: Numbers of speakers of Australian Indigenous languages (various surveys)' in 'Appendix F NILS endangerment and absolute number results' in McConvell, Marmion and McNicol 2005, pages 198-230 (PDF, 2.5MB).